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  • 2010-2014  (25)
  • 1985-1989  (3,492)
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  • Organic Chemistry  (7,780)
  • ddc:510
  • ddc:620
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  • 1
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    Supporting Global Numerical Optimization of Rational Functions by Generic Symbolic Convexity Tests (2010)
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    Publication Date: 2020-12-11
    Description: Convexity is an important property in nonlinear optimization since it allows to apply efficient local methods for finding global solutions. We propose to apply symbolic methods to prove or disprove convexity of rational functions over a polyhedral domain. Our algorithms reduce convexity questions to real quantifier elimination problems. Our methods are implemented and publicly available in the open source computer algebra system REDUCE. Our long term goal is to integrate REDUCE as a workhorse'' for symbolic computations into a numerical solver.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 2
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    Fault-Tolerant and Decentralized Lease Coordination in Distributed Systems (2010)
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    Publication Date: 2016-06-30
    Description: Applications which need exclusive access to a shared resource in distributed systems require a fault-tolerant and scalable mechanism to coordinate this exclusive access. Examples of such applications include distributed file systems and master/slave data replication. We present Flease, an algorithm for decentralized and fault-tolerant lease coordination in distributed systems. Our algorithm allows the processes competing for a resource to coordinate exclusive access through leases among themselves without a central component. The resulting system easily scales with an increasing number of nodes and resources. We prove that Flease ensures exclusive access, i.e. guarantees that there is at most one valid lease at any time.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 3
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    Robust Tail Assignment (2010)
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    Publication Date: 2020-08-05
    Description: We propose an efficient column generation method to minimize the probability of delay propagations along aircraft rotations. In this way, delay resistant schedules can be constructed. Computational results for large-scale real-world problems demonstrate substantial punctuality improvements. The method can be generalized to crew and integrated scheduling problems.
    Keywords: ddc:510
    Language: English
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  • 4
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    State Trajectory Compression for Optimal Control with Parabolic PDEs (2010)
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    Publication Date: 2022-01-07
    Description: In optimal control problems with nonlinear time-dependent 3D PDEs, full 4D discretizations are usually prohibitive due to the storage requirement. For this reason gradient and quasi-Newton methods working on the reduced functional are often employed. The computation of the reduced gradient requires one solve of the state equation forward in time, and one backward solve of the adjoint equation. The state enters into the adjoint equation, again requiring the storage of a full 4D data set. We propose a lossy compression algorithm using an inexact but cheap predictor for the state data, with additional entropy coding of prediction errors. As the data is used inside a discretized, iterative algorithm, lossy coding maintaining an error bound is sufficient.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 5
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    A simple mathematical model of the bovine estrous cycle: follicle development and endocrine interactions (2010)
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    Publication Date: 2020-03-11
    Description: Bovine fertility is the subject of extensive research in animal sciences, especially because fertility of dairy cows has declined during the last decades. The regulation of estrus is controlled by the complex interplay of various organs and hormones. Mathematical modeling of the bovine estrous cycle could help in understanding the dynamics of this complex biological system. In this paper we present a mathematical model of the bovine estrous cycle that includes the processes of follicle and corpus luteum development and the key hormones that interact to control these processes. Focus in this paper is on development of the model, but also some simulation results are presented, showing that a set of equations and parameters is obtained that describes the system consistent with empirical knowledge. Even though the majority of the mechanisms that are included are only known qualitatively as stimulatory or inhibitory effects, the model surprisingly well features quantitative observations made in reality. This model of the bovine estrous cycle could be used as a basis for more elaborate models with the ability to study effects of external manipulations and genetic differences.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 6
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    Rapid Learning for Binary Programs (2010)
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    Publication Date: 2022-03-14
    Description: Learning during search allows solvers for discrete optimization problems to remember parts of the search that they have already performed and avoid revisiting redundant parts. Learning approaches pioneered by the SAT and CP communities have been successfully incorporated into the SCIP constraint integer programming platform. In this paper we show that performing a heuristic constraint programming search during root node processing of a binary program can rapidly learn useful nogoods, bound changes, primal solutions, and branching statistics that improve the remaining IP search.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 7
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    Dynamic routing at different layers in IP-over-WDM networks -- Maximizing energy savings (2010)
    Details
    Publication Date: 2020-08-05
    Description: We estimate potential energy savings in IP-over-WDM networks achieved by switching off router line cards in low-demand hours. We compare three approaches to react on dynamics in the IP traffic over time, FUFL, DUFL and DUDL. They provide different levels of freedom in adjusting the routing of lightpaths in the WDM layer and the routing of demands in the IP layer. Using MILP models based on three realistic network topologies as well as realistic demands, power, and cost values, we show that already a simple monitoring of the lightpath utilization in order to deactivate empty line cards (FUFL) brings substantial benefits. The most significant savings, however, are achieved by rerouting traffic in the IP layer (DUFL), which allows emptying and deactivating lightpaths together with the corresponding line cards. A sophisticated reoptimization of the virtual topologies and the routing in the optical domain for every demand scenario (DUDL) yields nearly no additional profits in the considered networks. These results are independent of the ratio between the demand and capacity granularities, the time scale and the network topology, and show little dependency on the demand structure.
    Keywords: ddc:620
    Language: English
    Type: reportzib , doc-type:preprint
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  • 8
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    Models for Line Planning with Transfers (2010)
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    Publication Date: 2020-08-05
    Description: We propose a novel integer programming approach to transfer minimization for line planning problems in public transit. The idea is to incorporate penalties for transfers that are induced by “connection capacities” into the construction of the passenger paths. We show that such penalties can be dealt with by a combination of shortest and constrained shortest path algorithms such that the pricing problem for passenger paths can be solved efficiently. Connection capacity penalties (under)estimate the true transfer times. This error is, however, not a problem in practice. We show in a computational comparison with two standard models on a real-world scenario that our approach can be used to minimize passenger travel and transfer times for large-scale line planning problems with accurate results.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 9
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    Adaptive Timestep Control for the Contact-Stabilized Newmark Method (2010)
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    Publication Date: 2016-06-09
    Description: The aim of this paper is to devise an adaptive timestep control in the contact--stabilized Newmark method (CONTACX) for dynamical contact problems between two viscoelastic bodies in the framework of Signorini's condition. In order to construct a comparative scheme of higher order accuracy, we extend extrapolation techniques. This approach demands a subtle theoretical investigation of an asymptotic error expansion of the contact--stabilized Newmark scheme. On the basis of theoretical insight and numerical observations, we suggest an error estimator and a timestep selection which also cover the presence of contact. Finally, we give a numerical example.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 10
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    Railway capacity auctions with dual prices (2010)
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    Publication Date: 2020-08-05
    Description: Railway scheduling is based on the principle of the construction of a conflict-free timetable. This leads to a strict definition of capacity: in contrast with road transportation, it can be said in advance whether a given railway infrastructure can accommodate - at least in theory - a certain set of train requests. Consequently, auctions for railway capacity are modeled as auctions of discrete goods -- the train slots. We present estimates for the efficiency gain that may be generated by slot auctioning in comparison with list price allocation. We introduce a new class of allocation and auction problems, the feasible assignment problem, that is a proper generalization of the well-known combinatorial auction problem. The feasible assignment class was designed to cover the needs for an auction mechanism for railway slot auctions, but is of interest in its own right. As a practical instance to state and solve the railway slot allocation problem, we present an integer programming formulation, briefly the ACP, which turns out to be an instance of the feasible assignment problem and whose dual problem yields prices that can be applied to define a useful activity rule for the linearized version of the Ausubel Milgrom Proxy auction. We perform a simulation aiming to measure the impact on efficiency and convergence rate.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 11
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    Solving Optimal Control Problems with the Kaskade 7 Finite Element Toolbox (2010)
    Details
    Publication Date: 2022-01-07
    Description: This paper presents concepts and implementation of the finite element toolbox Kaskade 7, a flexible C++ code for solving elliptic and parabolic PDE systems. Issues such as problem formulation, assembly and adaptivity are discussed at the example of optimal control problems. Trajectory compression for parabolic optimization problems is considered as a case study.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 12
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    Aggregation Methods for Railway Networks (2010)
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    Publication Date: 2020-08-05
    Description: In this paper a bottom-up approach of automatic simplification of a railway network is presented. Starting from a very detailed, microscopic level, as it is used in railway simulation, the network is transformed by an algorithm to a less detailed level (macroscopic network), that is sufficient for long-term planning and optimization. In addition running and headway times are rounded to a pre-chosen time discretization by a special cumulative method, which we will present and analyse in this paper. After the transformation we fill the network with given train requests to compute an optimal slot allocation. Then the optimized schedule is re-transformed into the microscopic level and can be simulated without any conflicts occuring between the slots. The algorithm is used to transform the network of the very dense Simplon corridor between Swiss and Italy. With our aggregation it is possible for the first time to generate a profit maximal and conflict free timetable for the corridor across a day by a simultaneously optimization run.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 13
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    Merging solutions of non-linear algebraic systems (2010)
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    Publication Date: 2020-12-11
    Description: In solving large polynomial algebraic systems that are too big for standard Gröbner basis techniques one way to make progress is to introduce case distinctions. This divide and conquer technique can be beneficial if the algorithms and computer programs know how to take advantage of inequalities. A further hurdle is the form of the resulting general solutions which often have unnecessarily many branches. In this paper we discuss a procedure to merge solutions by dropping inequalities which are associated with them and, if necessary, by re-parametrizing solutions. In the appendix the usefulness of the procedure is demonstrated in the classification of quadratic Hamiltonians with a Lie-Poisson bracket $e(3)$. This application required the solution of algebraic systems with over 200 unknowns, 450 equations and between 5000 and 9000 terms.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 14
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    A Dynamical Systems Approach for Static Evaluation in Go (2010)
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    Publication Date: 2020-12-11
    Description: In the paper arguments are given why the concept of static evaluation (SE) has the potential to be a useful extension to Monte Carlo tree search. A new concept of modeling SE through a dynamical system is introduced and strengths and weaknesses are discussed. The general suitability of this approach is demonstrated. A Remark: Among users of the Internet Go server KGS the abbreviation SE is used for 'Score Estimator'. Although different from 'Static Evaluation' a score estimator is easily obtained from static evaluation by adding up probabilities of chains to be alive at the end of the game or points to be owned by White or Black
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 15
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    Classification of integrable quadratic Hamiltonians on e(3) (2010)
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    Publication Date: 2020-12-11
    Description: Linear Poisson brackets on e(3) typical of rigid body dynamics are considered. All quadratic Hamiltonians of Kowalevski type having additional first integral of fourth degree are found. Quantum analogs of these Hamiltonians are listed.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 16
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    Classification of integrable super-systems using the SsTools environment (2010)
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    Publication Date: 2020-12-11
    Description: A classification problem is proposed for supersymmetric %scaling\/-\/in\-va\-ri\-ant evolutionary PDE that satisfy the assumptions of nonlinearity, nondegeneracy, and homogeneity. Four classes of nonlinear coupled boson\/-\/fermion systems are discovered under the weighting assumption $|f|=|b|=|D_t|=\oh$. The syntax of the \Reduce\ package \SsTools, which was used for intermediate computations, and the applicability of its procedures to the calculus of super\/-\/PDE are described.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 17
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    N=2 supersymmetric a=4-KdV hierarchy derived via Gardner's deformation of Kaup-Boussinesq equation (2010)
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    Publication Date: 2020-12-11
    Description: We consider the problem of constructing Gardner's deformations for the $N{=}2$ supersymmetric $a{=}4$--\/Korteweg\/--\/de Vries equation; such deformations yield recurrence relations between the super\/-\/Hamiltonians of the hierarchy. We prove the non\/-\/existence %P.~Mathieu's Open problem on constructing for of supersymmetry\/-\/invariant %Gardner's deformations that %solutions, retract to Gardner's formulas for the KdV equation %whenever it is assumed that, under the %respective component reduction. % in the $N{=}2$ super\/-\/field. the solutions . At the same time, we propose a two\/-\/step scheme for the recursive production of the integrals of motion for the $N{=}2$,\ $a{=}4$--\/SKdV. First, we find a new Gardner's deformation of the Kaup\/--\/Boussinesq equation, which is contained in the bosonic limit of the super\/-\/%$N{=}2$,\ $a{=}4$--\/SKdV hierarchy. This yields the recurrence relation between the Hamiltonians of the limit, whence we determine the bosonic super\/- /Hamiltonians of the full $N{=}2$, $a{=}4$--\/SKdV hierarchy.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 18
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    The Quickest Path to the Goal (2010)
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    Publication Date: 2020-08-05
    Description: We provide an introduction into the mathematics of and with paths. Not on the shortest, but hopefully on an entertaining path!
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 19
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    Linienoptimierung - reif für die Praxis? (2010)
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    Publication Date: 2020-08-05
    Description: Wir stellen in dieser Arbeit ein mathematisches Optimierungsmodell zur Bestimmung eines optimalen Linienplans vor, das sowohl die Fahrzeiten und die Anzahl der Umstiege berücksichtigt als auch die Kosten des Liniennetzes. Dieses Modell deckt wichtige praktische Anforderungen ab, die in einem gemeinsamen Projekt mit den Verkehrsbetrieben in Potsdam (ViP) formuliert wurden. In diesem Projekt wurde der Linienplan 2010 für Potsdam entwickelt. Unsere Berechnungen zeigen, dass die mathematische Optimierung in nichts einer "Handplanung" des Liniennetzes nachsteht. Im Gegenteil, mit Hilfe des Optimierungsprogramms ist es möglich, durch Veränderung der Parameter mehrere verschiedene Szenarien zu berechnen, miteinander zu vergleichen und Aussagen über minimale Kosten und Fahrzeiten zu machen.
    Keywords: ddc:510
    Language: German
    Type: reportzib , doc-type:preprint
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  • 20
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    Positions in the Game of Go as Complex Systems (2010)
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    Publication Date: 2020-12-11
    Description: The paper gathers evidence showing different dimensions of the game of Go: the continuous and discrete nature of the game and different types of relations between state variables happening on ultra local, local, regional, and global scales. Based on these observations a new continuous local model for describing a board position is introduced. This includes the identification of the basic variables describing a board position and the formulation and solution of a dynamical system for their computation. To be usable as a static evaluation function for a game playing program at least group-wide (regional)aspects will have to be incorporated.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 21
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    Railway Track Allocation by Rapid Branching (2010)
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    Publication Date: 2020-08-05
    Description: The track allocation problem, also known as train routing problem or train timetabling problem, is to find a conflict-free set of train routes of maximum value in a railway network. Although it can be modeled as a standard path packing problem, instances of sizes relevant for real-world railway applications could not be solved up to now. We propose a rapid branching column generation approach that integrates the solution of the LP relaxation of a path coupling formulation of the problem with a special rounding heuristic. The approach is based on and exploits special properties of the bundle method for the approximate solution of convex piecewise linear functions. Computational results for difficult instances of the benchmark library TTPLIB are reported.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 22
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    Optimizing the Simplon Railway Corridor (2010)
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    Publication Date: 2020-08-05
    Description: This paper presents a case study on a railway timetable optimization for the very dense Simplon corridor, a major railway connection in the Alps between Switzerland and Italy. Starting from a detailed microscopic network as it is used in railway simulation, the data is transformed by an automatic procedure to a less detailed macroscopic network, that is sufficient for the purpose of capacity planning and amenable to state-of-the-art integer programming optimization methods. In this way, the macroscopic railway network is saturated with trains. Finally, the corresponding timetable is re-transformed to the microscopic level in such a way that it can be operated without any conflicts among the slots. Using this integer programming based micro-macro aggregation-disaggregation approach, it becomes for the first time possible to generate a profit maximal and conflict free timetable for the complete Simplon corridor over an entire day by a simultaneous optimization of all trains requests. This also allows to to undertake a sensitivity analysis of various problem parameters.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 23
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    Analysis of a multi-scale asymptotic model for internal gravity waves in a moist atmosphere (2010)
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    Publication Date: 2016-06-09
    Description: The thesis presents the analysis of a reduced model for modulation of internal gravity waves by deep convective clouds. The starting point for the derivation are conservation laws for mass, momentum and energy coupled with a bulk micro-physics model describing the evolution of mixing ratios of water vapor, cloud water and rain water. A reduced model for the identified scales of the regime is derived, using multi-scale asymptotics. The closure of the model employs conditional averaging over the horizontal scale of the convective clouds. The resulting reduced model is an extension of the anelastic equations, linearized around a constant background state, which are well-known from meteorology. The closure of the model is achieved purely by analytical means and involves no additional physically motivated assumptions. The essential new parameter arising from the coupling to a micro-physics model is the area fraction of saturated regions on the horizontal scale of the convective clouds. It turns out that this parameter is constant on the employed short timescale. Hence the clouds constitute a constant background, modulating the characteristics of propagation of internal waves. The model is then investigated by analytical as well as numerical means. Important results are, among others, that in the model moisture (i) inhibits propagation of internal waves by reducing the modulus of the group velocity, (ii) reduces the angle between the propagation direction of a wave-packet and the horizontal, (iii) causes critical layers and (iv) introduces a maximum horizontal wavelength beyond which waves are no longer propagating but become evanescent. The investigated examples of orographically generated gravity waves also feature a significant reduction of vertical momentum flux by moisture. The model is extended by assuming systematically small under-saturation, that is saturation at leading order. The closure is similar to the original case but requires additional assumptions. The saturated area fraction in the obtained model is no longer constant but now depends nonlinearly on vertical displacement and thus on vertical velocity.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 24
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    A Constraint Integer Programming Approach for Resource-Constrained Project Scheduling (2010)
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    Publication Date: 2022-03-14
    Description: We propose a hybrid approach for solving the resource-constrained project scheduling problem which is an extremely hard to solve combinatorial optimization problem of practical relevance. Jobs have to be scheduled on (renewable) resources subject to precedence constraints such that the resource capacities are never exceeded and the latest completion time of all jobs is minimized. The problem has challenged researchers from different communities, such as integer programming (IP), constraint programming (CP), and satisfiability testing (SAT). Still, there are instances with 60 jobs which have not been solved for many years. The currently best known approach, lazyFD, is a hybrid between CP and SAT techniques. In this paper we propose an even stronger hybridization by integrating all the three areas, IP, CP, and SAT, into a single branch-and-bound scheme. We show that lower bounds from the linear relaxation of the IP formulation and conflict analysis are key ingredients for pruning the search tree. First computational experiments show very promising results. For five instances of the well-known PSPLIB we report an improvement of lower bounds. Our implementation is generic, thus it can be potentially applied to similar problems as well.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 25
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    Coupling Meshbased and Meshfree Methods by a Transfer Operator Approach (2010)
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    Publication Date: 2023-11-03
    Description: In contrast to the well known meshbased methods like the finite element method, meshfree methods do not rely on a mesh. However besides their great applicability, meshfree methods are rather time consuming. Thus, it seems favorable to combine both methods, by using meshfree methods only in a small part of the domain, where a mesh is disadvantageous, and a meshbased method for the rest of the domain. We motivate, that this coupling between the two simulation techniques can be considered as saddle point problem and show the stability of this coupling. Thereby a novel transfer operator is introduced, which interacts in the transition zone, where both methods coexist.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 26
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720101
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  • 27
    Electronic Resource
    Electronic Resource
    The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1-13 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half-chair conformation, respectively, with ring C 1,3-diplanar in I (solid-state structure as determined by X-ray crystallography) and in chair conformation in II. A complete assignment of the 1H- and 13C-NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low-temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720102
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  • 28
    Electronic Resource
    Electronic Resource
    Palladium(0)-Catalyzed Cyclizations of Simple 1-Aryl-1,7-octadien-3-yl Acetates. Preliminary communicationPresented (W.O.) at the ‘3e Congrès national de la Société Française de Chimie’, Nice, September 5, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 14-16 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)-l-methylidene-2-styrylcyclopentanes 4 in the presence of 7 mol-% of [Pd(PPh3)4].
    Additional Material: 1 Tab.
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  • 29
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    Über den Einfluss des Akzeptor-Teilchromophors bei Dimethin-merocyanin-Farbstoffen auf das Aggregationsverhalten in wässriger Lösung (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 17-28 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Influence of the Acceptor Part of the Chromophor of Dimethinemerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long-chain alkyl-dimethinemerocyanine dyes containing sulfonate groups is synthesized in good yield and their aggregation tendency in H2O and in organic solvent/H2O mixtures investigated. The merocyanine dyes 11 and 15 only exhibit an intense, red-shifted absorption band due to J-aggregation in H2O without addition of salt. The influence of cationic and anionic tensides and other compounds as urea, glucose, and polysaccharides upon the J-aggregation tendency is investigated.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720104
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  • 30
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    Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 29-40 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.
    Additional Material: 1 Ill.
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  • 31
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    A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 59-64 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction between the chiral allenic acid (+)-(S)-1 and the carbodiimides 2a-d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3-5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.
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    URL: http://dx.doi.org/10.1002/hlca.19890720108
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  • 32
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    Konkurrenz von Endoperoxid- und Hydroperoxid-Bildung bei der Umsetzung von Singulett-Sauerstoff mit cyclischen, konjugierten Dienen. Teil I (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 51-58 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated DienesRose-bengal-sensitized photooxygenation of (-)-(R)-α-phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis-(3S, 6R)-epidioxy-p-menthene (2) and trans-(3R, 6S)-epidioxy-p-menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper-oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β-p-mentha-2,5-dien-1β-yl hydroperoxide (4) (14%), 4β-p-mentha-2,5-dien-1α-yl hydroperoxide (5) (9%), (2R, 4R)-p-mentha-1(7), 5-dien-2-yl hydroperoxide (6) (2,1%), (2S, 4R)-p-mentha-1(7),5-dien-2-yl hydroperoxide (7) (1,5%) and (1R)-p-mentha-3,6-dien-yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at -50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.
    Additional Material: 2 Ill.
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    Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 41-50 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
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    URL: http://dx.doi.org/10.1002/hlca.19890720106
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  • 34
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    Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazinesDedicated to Prof. Dr. C. H. Brieskorn (Würzburg, FRG) on the occasion of his 75th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 65-72 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Vinylindole (1a) and its donor- and acceptor-substituted (E)-derivatives 1b-e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (3) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b, 5, and 6. The reactions of the structurally related 3-vinylindoles 2a-e with 3 also gave rise to new indol-3-ylpyridazines 8, 9, and 10. The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.
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    URL: http://dx.doi.org/10.1002/hlca.19890720109
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  • 35
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    Photochemistry of Thiophen-2(5H)-onesDedicated to Prof. Dr. O. E. Polansky on the occasion of his 70th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 83-92 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording α, β-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropane-methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 2] cycloadducts 14 albeit in very low yields.
    Additional Material: 1 Tab.
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  • 36
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    Electronic and Molecular Structure of the C8H10+· Valence Isomers 1,3,5-Cyclooctatriene+· and Bicyclo[4.2.0]octa-2,4-diene+· from their Electronic absorption Spectra in Freon (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 73-82 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular cations of 1,3,5-cyclooctatriene (COT+·) and bicyclo[4.2.0]octa-2,4-diene (BCO+·) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon-glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.
    Additional Material: 2 Ill.
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  • 37
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    Cyclization Studies with N-Mannich bases of 2-substituted indoles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 93-100 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the indoles 7, 15, 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27, 28) and eight-membered rings (→ 29) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.
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    URL: http://dx.doi.org/10.1002/hlca.19890720112
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  • 38
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    Template-Dependent Incorporation of Spin-Labeled Thymidine Analogs into Viral DNA (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 110-116 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T-4 DNA polymerase using lambda-phage DNA as template. The template-dependent incorporation of the substrates was established by radio-labeling and ESR experiments.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720114
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  • 39
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    Stereoselektive Synthesen von Taxan-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 101-109 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Synthesis of Taxane DerivativesSubstituted racemic 4,8,12-trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro-aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.
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    URL: http://dx.doi.org/10.1002/hlca.19890720113
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  • 40
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    Asymmetric Diels-Alder reactions: X-Ray crystal-structure analysis of [N-((E)-But-2-enoyl)bornane-10,2-sultam]tetrachlorotitaniumPresented (WO) at the Annual Congress of the Royal Society of Chemistry, Canterbury, April, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 123-130 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An X-ray diffraction analysis of the crystalline complex 2b (MLn — TiCl4) shows a chelation of the carbonyl O-atom and the upper SO2 O-atom by TiCl4, a slightly pyramidal N-atom, and a π -face-stereoselective shielding of the C(α)-Si face by the CH2(3) group. The Ti-atom is in a pseudo-octahedral environment.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720116
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  • 41
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    Metal Complexes with Macrocyclic Ligands. Part XXVIIPart XXVI. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 131-138 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray structures of the Cu2+ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5, it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH-] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH 〉 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH- attack and the results of the X-ray structure analyses.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720117
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  • 42
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    A New Method for the Preparation of (E)-3-Acylprop-2-enoic AcidsPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988.Dedicated to Prof. R. E. Ireland on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 117-122 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for the preparation of (E)-3-acylprop-2-enoic acids ( = (E)-3-acylacrylic acids) of type II via acid-catalyzed isomerization of the corresponding 3-acylprop-2-ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720115
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  • 43
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    6-Thia-1-aza-5λ5-phosphabicyclo[3.2.0]hept-3-ene und Isothiocyanatophosphin-sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen- oder Ethylen-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 139-146 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives(Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a, b, and acrylates yield isothio-cyanatophosphin-sulfides 5a-c. The structures of 4a and 5a are proven by an X-ray diffraction analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720118
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  • 44
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    C45 und C50-Carotinoide. 6. Mitteilung5. Mitteilung, s. [1]. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotin) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 151-157 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C45- and C50-Carotenoids: Synthesis of an Optically Active Cyclic C20-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotene)The synthesis of the optically active cyclic C20-building block (R, R)-15 and of the optically active C50-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin (1) starting from (-)-β-pinene ((S)-2) is reported.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720120
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  • 45
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    Formation of the First Trimeric Monoterpenoid Indole Alkaloids (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 147-150 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3-hydroxy-14′-(3α″-tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′-(3α″-tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.
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    URL: http://dx.doi.org/10.1002/hlca.19890720119
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  • 46
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    Polynuclear Iron and Rhodium Complexes of 7-Oxa[2.2.1]hericene (2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 158-164 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: μ-Carbonyl(Rh—Rh)di(η5-indenyl)[(2R,3S)-C,2,3,C-η-(2,3,4,5-tetramethylidenebicyclo[2.2.1]heptan-7-one)]]-dirhodium(I)(Rh—Rh) (7) and cis-μ-[(2R,3S,5R,6S))-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis[μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis-μ-[(2R,3S,5R,6S] (9), trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η: C,5,6, C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)-μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)-(tricarbonyliron) (10), and, μ-carbonyl(Rh—Rh)[(2R,3S)-C,2,3,C-η-(2,3-dimethyl-5,6-dimethylidenebicyclo-[2.2.1]hept-2-en-7-one)]di(η5-indenyl)dirhodium(I)(Rh—Rh) (11). Treatment of 7-oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis-μ-[(2R,3S,5R,6S)-] (12) and trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis(tricarbonyliron)(13).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720121
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  • 47
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    Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 172-179 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-onesThe reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.
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    Synthesis of the Oviposition-Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 165-171 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the assignment of the configuration at C(8) and C(15) of the natural oviposition-deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)-4 and (5S)-4 with the boron enolates of the C10 building blocks (4S)-13 and (4R)-13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)-1, (8R,15R)-1, (8R,15S)-1, and (8S,15S)-1 (Scheme 6).
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  • 49
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    Mitteilungen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 185-192 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720125
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  • 50
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    New Spermine Alkaloids from Aphelandra tetragona (VAHL) NEESDedicated to Prof. Dr. D. Gröger on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 180-184 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 18-O-Methylchaenorpine (1a) and iso-18-O-methylchaenorpine (1b) two novel stereoisomeric spermine alkaloids were isolated from the roots of Aphelandra tetragona (VAHL) NEES. Their structures were established by chemical and spectroscopic studies.
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    URL: http://dx.doi.org/10.1002/hlca.19890720124
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    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720201
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  • 52
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    1,5,7-Triazabicyclo[4.4.0]dec-5-en als Reaktionsmedium: Präparativ ergiebige einstufige Herstellung von Etioporphyrin aus Protoporphyrin (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 185-195 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,5,7-Triazabicyclo[4.4.0]dec-5-ene as Reaction Medium: An Efficient One-Step Formation of Etioporphyrine from ProtoporphyrineHeating the commercially available protoporphyrine (4) in molten 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 200° for 4 h under exclusion of O2 produces etioporphyrine (6) in 60-70% yield by bisdecarboxylation and concomitant reduction of the two vinyl groups. Mesoporphyrine (5) is bisdecarboxylated to 6 in over 80% yield under these conditions in TBD as well as in DBU as the reaction medium.
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  • 53
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    The Chemistry of Thujone. Part XIV.Part XIII [1]. Synthesis of biologically active aryl terpenoid analogues (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 205-212 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Employing thujone-derived intermediates, a series of achiral (9a-d; Scheme 1) and chiral (11b and 11d; Scheme 2) terpene analogues related to the biologically active ‘terpenoid’ hybrids have been prepared. The stereochemistry of the key epoxidation reaction was established by correlation of the product 11b with the previously reported alcohol (R)-20 of known absolute configuration (Scheme 3).
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  • 54
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    Vinyl Carbanions. Part 36.Part 35: [9]. Synthesis of 3-deoxy-D-manno-2-octulosonic acid (KDO) and derivatives (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 213-223 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The β-C-lithiated acrylamide 3A has been proven to be an ideal pyruvate β-carbanion equivalent useful in a highly diastereoselective KDO synthesis. The starting material 3 was prepared from pyruvate diethyl acetal in four convenient steps. Direct lithiation with 2 equiv. of LDA generated the dilithiated species 3A quantitatively. Reaction with 2,3:4,5-di-O-isopropylidene-D-arabinose (11) was highly D-manno-selective. The product 12 was obtained readily from the reaction mixture via crystallization. Ring closure to the butenolide 13, subsequent PhS-group removal with Bu3SnH and pyridinium bromide, and hydrogenolytic debenzylation afforded the known butenolide 19; this KDO precursor gives KDO in two convenient steps. Butenolide 19 was also transformed via two high-yielding steps into the 4,5:7,8-di-O-cyclohexylidene-KDO derivative 22, a valuable starting material for KDO α-glycoside syntheses.
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  • 55
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    Colchicine models: Synthesis and Antitubulin Activity of 2′-Monosubstituted and 2′, 5-Disubstituted 2,3,4,4′-Tetramethoxy-1,1′-biphenyls. Synthesis of 4,4′, 5′, 6′-tetramethoxy-1,1′-biphenyl-2,3′-dicarboxylic acidThis paper is dedicated to our friend and colleague Dr. Tetsuji Kametani, Hoshi College of Pharmacy, Tokyo, Japan, who died on October 11, 1988 (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 196-204 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reductive amination of 2,3,4,4′-tetramethoxtybiphenyl-2-carbaldehyde (4) with MeNH2 afforded methylamine 5 (Scheme 1), Hydroxymethylation of amine 8, prepared similarly from 4 by reductive amination with benzylamine followed by N-methylation, afforded alcohol 12 which was converted the 5-methyl-substituted methylamine 14 by conventional chemical reactions (Scheme 2), Methylamine 14 was also obtained from ester 16 after hydroxymethylation to alcohol 17 and conventional manipulation of alcohol and ester functions (Scheme 2). Both amines 5 and 14 as well as the 2′, 5-dimethyl-substituted biphenyl 26 prepared from the dialdehyde 25 by a Wolff-Kishner reduction, did not show noteworthy activity in the tubulin binding assay or as inhibitors of tubulin polymerization (Table). However, the 2′ethyl-substituted biphebyl 11 prepared from 4 by reaction with MeLi followed by dehyderation and catalytic reduction of styrene 10 (Scheme 1) showed appreciable activity in both assays, coming close to that of known phenyltropolone models. The X-ray analysis of 14·HCl and 11 showed significant difference in the orientation of the rings with respect to one another (Fig.).
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    Biosynthesis of Homoterpenes in Higher Plants (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 247-253 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In higher plants, the two homoterpenes 4,8-dimethyinona-1,3,7-triene (1) and 4,8,12-trimethyltrideca-1,3,7,11-tetraene (2) are synthesized from the regular terpene alcohols nerolidol and geranyllinalool by fragmentation into the homoterpene and butenone. The biosynthetic pathway is evidenced by conversion of (2H)nerolidol in Hoya purpureo-fusca, Magnolia liliiflora nigra, Robinia pseudoacacia, and Philadelphus coronarius.
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    URL: http://dx.doi.org/10.1002/hlca.19890720208
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  • 57
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    Sphinxolide, a 26-Membered Antitumoral Macrolide Isolated from an Unidentified Pacific Nudibranch (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 237-246 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that an unidentified nudibranch of Hawaiian waters contains a 26-membered macrolide, sphinxolide ((-)-1) with potent activity against the KB cell line. The structure of sphinxolide, a 2:1 mixture of (E/Z)-isomers at the formamide moiety, is established to be (-)-1 on the basis of extensive NMR and FAB-MS analysis, in combination with data for the products of mono- (→(-)-2) and diacetylation (→(+)-3).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720207
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  • 58
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    Synthesis of Aristotelia-Type Alkaloids.Part III: [1]. Part IV. Synthesis of (±)-aristoserratineDedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 254-263 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convergent diastereoselective synthesis of racemic aristoserratine ((±)-24) via an intramolecular iminium-ion cyclization is described. The pivotal imine (±)-19 was prepared by condensation of the two building blocks (± )-trans-8-amino-3-(2,6-difluorobenzyloxy)-1-p-menthene ((±)-11) and N-(p-methoxybenzenesulfonyl)-3-indo-leacetaldehyde (18) which were synthesized from (±)-trans-1-p-menthene-3,8-diol ((±)-7) and 3-indoleacetic acid, respectively. On the route to the target (±)-24, two previously unknown indole alkaloids have been characterized, namely (±)-‘anti’-hobartin-15-ol ((±)-22) and (±)-‘anti’-aristotelin-15-ol ((±)-23).
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720209
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  • 59
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    Syntheses of α, β-Epoxy Silyl Ketones (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 264-270 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the α, β-epoxy-acylsilanes 1 and 2 starting from the allylic silyl alcohols (E)- and (Z)-3, respectively, by epoxidation with t-BuOOH/VO(acac)2 followed by oxidation with Collins reagent (CrO3/pyridine) in up to 70% overall yields, is described. The acid-catalyzed rearrangement of the epoxy-silyl alcohols 4A + B und 5A + B led to the novel unstable diastereoisomeric α-silyl-β-hydroxy-aldehydes 9 and 10, respectively. The structure of 10 was established by X-ray crystal-structure analysis of the corresponding alcohol 11.
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    URL: http://dx.doi.org/10.1002/hlca.19890720210
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    Spectroscopic Studies of Cyclometallated Pd(II) and Pt(II) Complexes: Optical absorption and emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 224-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polarized optical absorption and emission (spectra, decay times) of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (thpy ≡ C(3′)-deprotonated form of 2-(2-thienyl)pyridine) at temperatures 1.9 K ≤ T ≤ 80 K are reported. The emission of [Pt(thpy)2] can be influenced strongly by applied magnetic fields (0 ≤ H ≤ 6 T). Depending on the central ions Pd and Pt, the lowest excited electronic states of the single complexes are ligand-centered (LC) states and metal-to-ligand charge transfer (MLCT) states, respectively. This difference leads to distinctly dissimilar properties of the emission of both compounds. The experimental data show that the emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] at T ≤ 30 K originates from several types of traps (defect states of symmetry 3B2-stabilized below the exciton band) with LC and MLCT character, respectively. In the Pt compound, the 3B2 is split by spin-orbit coupling into three states. The states B1′ and A2′, which determine the emission properties, are separated by Δv ∼ 13 cm-1. Both states can mix under the influence of an applied magnetic field yielding an increase of the emission intensity by a factor of ∼ 1.5 at H = 6 T.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720206
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    Total Synthesis of L-Allose, L-Talose, and derivatives.Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’ [2]) as synthetic intermediates, Part IV. Part III, see [1]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 278-286 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1S, 4R, 5S, 6S)-5-exo, 6-exo-(Isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((-)-1) was transformed with high stereoselectivity to L-allose. Similarly, enantiomer (+)-1 was transformed into L-talose. The ketones (+)-1 and (-)-1 were derived from furan and 1-cyanovinyl (1S)-camphanate and 1-cyanovinyl (1R)-camphanate, respectively.
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    URL: http://dx.doi.org/10.1002/hlca.19890720212
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    Highly Stereoselective Total Syntheses of 2,5-Anhydro-4-deoxy-D-ribo-hexonic Acid and of (1S)-1-C-(6-amino-7H-purin-8-yl)-1,4-anhydro-3-deoxy-D-erythro-pentitol (= cordycepin C)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’) as synthetic intermediates, Part V. Part III: [1]. Part IV: [2].Part of the planned Ph. D. thesis of F. G., University of Lausanne.Dedicated to Prof. Hans Dahn on the occasion of his 70th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 271-277 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly regio- and stereoselective monohydroxylation of the C=C bond of (+)-7-oxabicyclo[2.2.1]hept-5-en-2-one (8) was achieved via LiAlH4 reduction of the corresponding 5,6-exo-epoxy dimethyl acetal 9. The reaction gave exclusively (-)-(1R, 2R, 4S)-6,6-dimethoxy-7-oxabicyclo[2.2.1]heptan-2-exo-ol (10) which was transformed into 2,5-anhydro-3-O-benzyl-4-deoxy-D-ribo-hexonic acid (15) and 2,5-anhydro-4-deoxy-D-ribo-hexonic acid (6) via ozonolysis of (-)-(1R, 4S, 6R)-6-exo-benzyloxy-2-{[(tert-butyl)dimethylsilyl]oxy}-7-oxabicyclo[2.2.1]hept-2-ene (14). Cordycepin C (5) was derived from 6 and 4,5,6-triaminopyrimidine using CsF/DMF to generate the adenine heterocycle.
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    Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher HerkunftDr. G. Ohloff zum 65. Geburtstag mit den besten Wünschen gewidmet (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 287-294 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Absolute Configuration of Iridals and Cycloiridals of Different OriginNatural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C31-triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco-ring-A iridal has the same stereo-chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.
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    URL: http://dx.doi.org/10.1002/hlca.19890720213
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    Metal Complexes with Macrocyclic Ligands. Part XXVIII.Part XXVII: [1]. Structures and stabilities of the Cu2+ complexes with 1,4,7-triazacyclononane-1-acetic acid (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 307-312 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric study of the complexation of 1,4,7-triazacyclononane-l-acetic acid (1) with Cu2+ (I = 0.5 (KNO3), T = 25°) indicates the presence of the species [Cu(1)], [Cu(1)OH], [Cu(1)2], and [(Cu(1))2OH], the stability constants of which are determined. The two complexes [Cu(1)]ClO4 and [(Cu(1)2)OH]ClO4 were also characterized by X-ray structure analysis. In both cases, the Cu2+ ion is in a distorted square-pyramidal arrangement, penta-coordinated by the three N-atoms of the macrocycle, an O-atom of the carboxylate, and an additional O-atom either from a second carboxylate or from an OH-, acting as a bridge between two metal centres.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720215
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    Metal Complexes with Macrocyclic Ligands. Part XXIX.Part XXVIII: [1]. Structural and kinetic studies of two isomeric Cu2+ complexes with 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 313-319 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and complexation properties of 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetra-decane (2) are described. This ligand forms with Cu2+ two complexes, one of which has been characterized by X-ray structure analysis. The structural, spectral, and kinetic studies indicate that the two Cu2+ complexes are isomers with the macrocycle in the trans-III and trans-I configuration. The rate of the interconversion of the trans-I isomer to the thermodynamically more stable trans-III species is proportional to [OH-]. A mechanism for this reaction is proposed.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720216
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    Stereochemical Criteria Providing Unambiguous Experimental Evidence for the intermediacy of ion/molecule complexes in the generation of enolates from gaseous alkoxides. Short communicationDedicated to Prof. Josef Seibl on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 320-322 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The epimeric alkoxides 6a and 6b, generated in the gas phase by deprotonation of the stereospecifically deuterated isoborneols 5a and 5b, undergo loss of H2 and HD in a 1:1 ratio. This result, ruling out a concerted one-step process, establishes the intermediacy of an ion/molecular complex (‘solvated’ hydride ion) in the course of formation of enolates from the alkoxide anions in the gas phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720217
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    Neue Dimethinmerocyanin-Farbstoffe mit der (Sulfobutyl)benzothiazol-Gruppe als Donor-Teilchromophor und deren Aggregationsverhalten in wässriger Lösung (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 295-306 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Dimethinemerocyanine Dyes with the (Sulfobutyl)benzothiazole Group as Donor Part of the Chromophor and their Aggregation Tendency in Aqueous SolutionA series of novel dimethinemerocyanine dyes with the (sulfobutyl)benzothiazole group as the donor part of the chromophor is synthesized in good yield and their aggregation tendency in H2O without addition of salt investigated. The merocyanine dye 2b only gives J-aggregation in H2O. The dyes 1a-f and 2a exhibit an intense, red-shifted absorption band due to J-aggregation in H2O in the presence of Me4NCl. In contrast, the dyes 1g and 2c-f show a slightly red-shifted absorption band. The degree of aggregation in H2O is investigated by ultracentrifugation of the representative 2e. Indeed, the slightly red-shifted absorption band in H2O is due to aggregation of ‘oligomers’ of the dye. Contrary to the aggregation of ‘polymers’ of dyes (J-aggregation), we suggest the term ‘K’ band for the slightly red-shifted absorption band. The hemicyanine dye 5 gives the same absorption band in MeOH and in MeOH/H2O 1:3. The dye 11 shows an absorption band in H2O that is probably blue-shifted because of negative solvatochromism. The merocyanine dye 13 gives H-aggregation in H2O.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720214
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  • 68
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    Models for Copper-Dioxygen Complexes: The chemistry of copper(II) with some planar tridentate nitrogen ligands (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 323-337 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2,6-bis(l-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2) 2,6-bis(benzothiazol-2-yl) pyridine (bzthpy, 3), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4), and 2,2′, 6′, 2″-terpyridyl (terpy, 5) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl- and OH- (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate-bridged dinuclear species.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720218
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  • 69
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    Synthesis of (-)-Conduritol C (1L-Cyclohex-5-ene-1,2,3/4-tetrol)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5en-2-yl derivatives (‘naked sugars’ [1]) as synthetic intermediates, Part VI; Part V:[2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 338-347 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1R, 2R, 4R)-2-endo-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate ((-)-7) has been transformed into the all-cis-configurated 4L-4,5,6/0-trihydroxycyclohex-2-en-1-one derivatives (-)-12 and (-)-19. (-)-Conduritol C ((-)-3) was derived in a stereospecific manner from (-)-12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720219
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  • 70
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    Diels-Alder-Reaktionen mit 3-Cyclopropylidenprop-1-enyl-ethyl-ether als 1,3-Dien (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 348-352 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diels-Alder Reactions with 3-Cyclopropylideneprop-1-enyl Ethyl Ether as 1,3-DieneThe title compound undergoes readily Diels-Alder reactions with various dienophiles, especially with quinones. The resulting adducts constitute key intermediates in the synthesis of labdane diterpenoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720220
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  • 71
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    Synthese von (+)-Abscisinsäure (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 361-364 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (+)-Abscisic Acid.Starting from (4S)-4-hydroxy-2,6,6-trimethylcyclohex-2-enone (2), a short synthesis of the natural (+)-abscisic acid ((+)-1) has been accomplished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720222
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  • 72
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    Ein neuer Zugang zu 2,6,6-Trimethylcyclohexa-2,4-dienon aus 4-Oxoisophoron (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 365-369 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Access to 2,6,6-Trimethylcyclohexa-2,4-dienone from 4-Oxoisophorone2,6,6-Trimethylcyclohexa-2,4-dienone (1), a versatile starting material for the preparation of some carotenoids and several natural products, was efficiently (73% yield) prepared from oxoisophorone 3. After conversion of 3 to the alcohol 4 or the acetate 5, H2O was eliminated (4→1) under acidic distillative conditions, whereas AcOH could be eliminated (5→l) under Pd(O) catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720223
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  • 73
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    Neue Zugänge zu einigen aromatischen Retinoiden (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 370-376 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Approaches to Some Aromatic RetinoidsStarting from 2,3,5-trimethylphenol (2), two pathways to ethyl (all-E)-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (1) and to some of its (Z)-isomers have been developed. The first one is based on a Pd(O)-catalyzed arylation of (Z)-3-methylpent-2-en-4-yn-l-ol (6) with 4-bromo-2,3,5-trimethylanisol (5). The acetylenic C15-alcohol 9 was transformed into the corresponding acetylenic phosphonium salt 10, which was catalytically hydrogenated to the olefinic Wittig salt. Wittig olefination led, then, to the (6Z, 8Z)- and (4Z, 6Z, 8Z)-isomers, 7 and 8, respectively. In a second approach, Friedel-Crafts reaction of 3-methylpent-l-en-4-yn-3-ol with the 2,3,5-trimethylanisol gave a C15-intermediate with a terminal C=C bond in the side chain. After deprotonation and reaction with a C5 aldehyd, the corresponding C20-intermediate could be isolated in high yield. Finally, further conversion led predominantly to the (all-E)-retinoid, accompanied by its (9Z)- and (13Z)-isomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720224
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  • 74
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    Synthesis of Gossypol AnaloguesDedicated to the memory of Professor Dr. Pierre Crabbé (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 353-360 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two gossypol analogues 2a and 2b were synthesized for biological evaluation as male contraceptive agents. The naphthol 8c was prepared by analogy with a known procedure starling from 3-isopropylcatechol (3). (t-Bu)2O2-Mediated phenolic coupling of 8c furnished the binaphthol 9c which, after pyrane ring closure, deprotection. and selective bisformylation with SnCl4/Cl2CHOCH3, gave the target compound 2a. The corresponding tetrahydroxy analogue 2b was prepared in a similar way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720221
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  • 75
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    Cyclometalated Compounds of Platinum(II) with two different C, N-aromatic ligands (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 377-382 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic route leading to bis-heteroleptic cyclometalated complexes is described. The complexes [2-(2′-thienyl)pyridinato-N, C-3′]{2-[3′-(trimethylsilyl)2′-thienyl]pyridinato-N, C3′}platinum(II) ([Pt(thpy) (TMS-thpy)]; I) and (l-phenylpyrazolato-N2, C2′)[2-(2′-thienyl)pyridinato-N, C3′]platinum ([Pt(Phpz)(thpy)]; II) are characterized by UV/VIS, NMR, and mass spectroscopy. Thermal and photochemical oxidative addition reactions yield two out of the 10 possible pairs of enantiomers of octahedral Pt(IV) compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720225
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    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720301
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  • 77
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    Mitteilungen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 401-402 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720228
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  • 78
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    The Radical Cations of Bicyclo[2.2.1]hepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and bicyclo[2.2.2]octa-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR studyPart 5 of ‘Applications of ENDOR Spectroscopy to Radical cations in Freon matrices’. Part-4: [1]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 383-390 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are -0.780 ±0.005, +0.304±0.002, and -0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = -0.594 ± 0.005, Ay= -0.913 ± 0.005, and Az = -0.834 ± 0.005 mT (x parallel to C—H- z parallel to 2pπ axis). For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are -0.68 ± 0.01, +0.162 ± 0.005, and -0.108 ± 0.005 mT, respectively. The hyperfine data for \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document} fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π-MO's.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720226
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  • 79
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    The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P-450Cath., Proceeding with retention of configurationPresented in part at the ‘22nd Reaction Mechanisms Conference’, Pittsburgh, 12.6-16.6.88, at the ‘6th International Conference on Biochemistry and Biophysics of Cytochrome P-450’, Vienna, 3.7.-8.7.88, and at the meeting on the ‘Biocatalytic synthesis of Organic Compounds’, Saratoga Springs, NY, 8.-12.8.88.Dedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 391-400 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incubation of the geraniols (R)-(8-2H1)[8-3H1]-1 and (S)-(8-2H1)[8-3H1]-1 with microsomal cytochrome P-450Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8-hydroxygeraniols (S)-(8-2H1)[8-3H1]-2 and (R)-(8-2H1)[8-3H1]-2. Their absolute configuration was assigned on the basis of the 1H-decoupled 3H-NMR Spectra of the corresponding dicamphanates (S)-(8-2H1)[8-3H1]-9 and (R)-(8-2H1)[8-3H1]-9, of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720227
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  • 80
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    Elektrochemische Decarboxylierung von L.-Threonin- und Oligopeptid-Derivaten unter Bildung von N-Acyl-N, O-acetalen: Herstellung von Oligopeptiden mit Carboxamid-oder Phosphonat-C-TerminusTeilweise in einer Kurzmitteilung erwähnt (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 401-425 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electrochemical Decarboxylation of L-Threonine and Oligopeptide Derivatives with Formation of N-Acyl-N, O-acetals: Preparation of Oligopeptides with Amide or Phophonate C-TerminusDerivatives of α-amino acids with two stereogenic centers (cf. L-threonine) and of di-, tri-, and tetrapeptides are electrolyzed in MeOH or AcOH, with formation of N-acyl-N, O-acetals (1b-15b, 20b), in an anodic oxidative substitution of the COOH by an OR group. The amine ends of the oligopeptides may be benzyloxycarbonyl(Z)- or (tert-butoxy)carbonyl(Boc)-protected. With unprotected dipeptides, an electrolytic decarboxylative cyclization to imidazolidinones (18c, 19c) may also occur (in H2O/NH4OAc). The electrolyses are carried out in simple flasks with cooling jackets (‘undivided cell’), using constant current conditions and anodes of Pt or glassy C. The electrolyte is generated in situ by adding 10-20 mol-% of a tertiary amine. Mild acidic hydrolysis of electrolysis products thus obtained may lead to amino-acid amides or peptide amides (10c, 11c, 12c, 17c) with one amino acid less than the starting material. The N, O-acetals from L-threonine and the oligopeptides also react with organometallic nucleophiles such as Grignard compounds (→21-26, 29), with formation of products in which the original COOH group has been replaced by alkyl or allyl (sometimes even with moderate stereoselectivity). By treatment of the peptide-derived (open-chain) N, O-acetals with trialkyl or triaryl phosphites/TiCl4 the RO group is replaced by a phosphodiester group in a (non-diastereoselective) Michaelis-Arbuzov-type reaction (1d, 1e, 2d-9d, 5e). Thus, the two-step sequence of electrolysis and phosphonation converts an oligopeptide derivative to an analogue with a phosphonic-acid end group. The diastereoisomeric N-protected dimethyl and diethyl dipeptidephosphonates (also prepared from the corresponding diaryl esters by Ti(OR)4-mediated transesterification) could be separated by preparative HPLC (SiO2, Lichrosorb Si 60, 10 μm); the dextrorotatory isomers of 1d-3d were assigned L, D-, the laevoratory ones L, L-configuration by hydrolysis to and identification of the known amino and aminophosphonic acids. The results described demonstrate a new simple route leading, from a given oligopeptide, to pure peptide analogues of known configuration.
    Notes: No abstract.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720302
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    Acid-Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3-Halofurans, Flavones, and StyrylchromonesPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 447-456 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetylenic acetals of type I (Scheme 1) and acetylenic ketones of type III (Scheme 1), 37 and 38 (Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid-catalyzed cyclization reactions. By this way, substituted 3-halofurans of type II and IV (Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good-to-excellent yields. The high degree of regioselectivity in the synthesis of the 3-halofurans (Scheme 4) is the result of the regioselective β-addition of HX (X = Cl, Br, I) to the acetylenic aldehyde and acetylenic ketone moieties. A possible mechanism is depicted in Scheme 5. Since 3-halofurans can easily be metalated and substituted, this approach constitutes a new synthesis of highly substituted furans.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720305
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  • 82
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    Stoffwechselprodukte von Mikroorganismen. 253. Mitteilung252, Mitteilung. Hormaomycin, ein neues Peptid-lacton mit morphogener Aktivität auf Streptomyceten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 426-437 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hormaomycin, a Novel Peptide Lactone with Morphogenetic Activity on StreptomycesA culture identified as Streptomyces griseoflavus (strain W-384) has been found to produce a novel peptide-lactone antibiotic designated hormaomycin (6). The empirical molecular formula of the compound is established to be C55H69ClN10O14. The constituent amino acids of the antibiotic are suggested to be allothreonine (1; 1), isoleucine (2; 1), 3-methyl-phenylalanine (3; 2), and, for the first time identified from a natural source, 4-[(Z)-prop-1-enyl]-proline (4; 1) and 3-(2-nitrocyclopropyl)-alanine (5; 2). The amino acids were delivered by acidic hydrolysis and assigned by high-resolution- GC/MS analysis (after transformation to derivatives) in combination with extended 2D-NMR experiments of the antibiotic itself. From the latter, it became plausible that the N-terminus of the peptide chain is acylated by a Cl-containing derivative of 1H-pyrrol-2-carboxylic acid. Hormaomycin is active against some Gram-positive bacteria. In addition, the antibiotic exhibits potent aerial mycelium-inducing activity and effects the production of antibiotics.
    Notes: No abstract.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720303
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    Novel Trinor-eremophilanes (Dendryphiellin B, C, and D), Eremophilanes (Dendryphiellin E, F, and G), and Branched C9-Carboxylic Acids (Dendryphiellic Acid A and B) from the Marine Deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 438-446 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further investigation of global extracts from cultures of the marine deuteromycete Dendryphiella salina leads to the isolation of three novel trinor-eremophilanes esterified by branched C9-carboxylic acids, dendryphiellin B(= (+)-(1R*,2S*,7R*,8aR*)-1,2,6,7,8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*, 2E, 4E)-6-hydroxy-6-methylocta-2,4-dienoate; (+)-2), dendryphiellin C (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7,8,8a-hexa-hydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6S, 2E, 4E)-6-methylocta-2,4-dienoate; (+)-3)), and dendryphiellin D (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7(8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*,2E,4E)-6-(hydroxymethyl)octa-2,4-dienoate; (+)-4). An intact eremophilane, dendryphiellin E (5), and its ethanolysis product dendryphiellin F whose absolute configuration is represented by structural formula (+)-6 are also isolated from the above extracts. Dendryphiellin E exists as an open form 5a in equilibrium with a closed form 5b. A similar equilibrium exists between the open form 8a and the closed form 8b of a non-esterified eremophilane, dendryphiellin G (8), which is isolated too from the above extracts and proves structurally related to the cyclic portion of 5. Finally, the free, branched C9-carboxylic acids dendryphiellic acid A ((+)-9) and B ((+)-10) which correspond to side chains of the above esterified terpenes are also isolated from the above extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720304
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    Eine neue Azepinring-Synthese (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 457-463 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Azepine-Ring SynthesisA new one-step synthesis of an azepine ring is described. The 2H-pyran-2-one ring of methyl cumalate (8) or cumalaldehyde (2) upon reaction with an 1-aminoacryl derivative, e.g. 1 or 6, is opened with subsequent decarboxylation to give a 1-aminobutadiene derivative that undergoes an electrocyclic ring closure to the azepine ring (Schemes 1 and 2).
    Notes: No abstract.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720306
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  • 85
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    New Hyperforin Derivatives from Hypericum revolutum VAHL with Growth-Inhibitory Activity against a Human Colon Carcinoma Cell LinePresented in part at the 36th Annual Congress on Medicinal Plant Research, Freiburg im Breisgau, FRG, 12-16th September, 1988, and at the Meeting of the Swiss Chemical Society, Bern, 21st October, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 464-471 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crude petroleum-ether extract of the root bark of Hypericum revolutum VAHL (Guttiferae) exhibited in vitro growth-inhibitory activity against the Co-115 human colon carcinoma cell line. Activity-guided fractionation of this extract resulted in the isolation of two new hyperforin derivatives 1 and 2. The structure of 1 (hyperevolutin A) was established by X-ray analysis as the 4-hydroxy-8-exo-methyl-5,7-exo-bis(3-methylbut-2-enyl)-1-(2-methyl-1-oxopropyl)-8-endo-(4-methylpent-3-enyl)bicyclo[3.3.1]non-3-ene-2,9-dione. The structure of the homologue 2 was deduced by comparison of its UV and 1H- and 13C-NMR spectra with those of 1.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720307
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  • 86
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    Asymmetric Diels-Alder Reaction of 1-Methoxybuta-1,3-diene with (2R)-N-Glyoxyloylbornane-10,2-sultam (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 482-486 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from sultam 1, the chiral dienophile (2R)-N-glyoxyloylbornane-10,2-sultam (4) was readily prepared. Non-catalyzed atmospheric- and high-pressure as well as [Eu(fod)3]-promoted [4 + 2] cycloadditions of 1-methoxy-buta-1,3-diene (5) to chiral dienophile 4, leading with high asymmetric induction to 6-methoxy-3,6-dihydro-2H-pyran-2-yl derivatives 6-9, are described. The extent and direction of asymmetric induction in these reactions were established by 1H-NMR analysis and chemical correlation, respectively. Stereochemical models for both non-catalyzed and [Eu(fod)3]-promoted reactions are proposed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720310
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  • 87
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    5,10:8,9-Disecosteroids (= Steroklastanes): A new type of modified steroidsDr. Günther Ohloff on the occasion of his 65th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 608-623 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermolysis of steroidal 5α, 8α- peroxides of type 3a-d generates as major products the corresponding diseco compounds containing a 14-membered ring instead of the standard A-B-C-ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β-unsaturated ketones of type 4, formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer-Villiger oxidation to give, as final products, the 15-membered cyclic epoxyenol lactones of type 20 and 21. The structures of the various products were determined by 1H- and 13C-NMR spectroscopy. The conformations of the 14- and 15-membered rings were established by X-ray structure analyses of 7 and 21a. A reaction mechanism for the above transformations is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720320
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  • 88
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    Thermal and Photochemical Reactions of 1,2-Annelated Barrelenes and Hydrobarrelenes in the presence of transition-metal carbonyls (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 648-652 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [Co2(CO)8]-mediated retro-Diels-Alder reaction of the annelated barrelenes 1 afforded the 1H-indol-2(3H)-one derivatives 3 (Scheme 1), while the hydrobarrelene 4a, under the same conditions, was converted to the anilide 6 (Scheme 2); 4b remained unaffected. The direct irradiation of 1 led to the annelated cyclooctatetraenes 7 (Scheme 3). On irradiation in the presence of excess of [Fe(CO)5], 1a, 1b, and 4a gave the tricarbonyliron complexes 8, 9, and 11, respectively (Schemes 3 and 4); under these conditions, 4b was inert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720404
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  • 89
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    A Simple and Efficient Method for the Preparation of Binaltrorphimine and Derivatives and determination of their K opioid antagonist selectivity (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 675-677 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bimorphinans 1 (binaltrorphimine), 3, and 7 have been prepared by treatment of the parent morphinan-6-ones naltrexone (5), naloxone (4), and dihydrocodeinone (6), respectively, with N-methylhydrazine sulfate in AcOH at room temperature. Compound 3 showed opioid antagonist potency and selectivity for K receptors which were somewhat lower in comparison to 1.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720408
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  • 90
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    Synthèse d'une sonde biotinylée à bras clivable allongé pour l'isolement des récepteurs de l'angiotensine II (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 678-689 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors PurificationWe have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl-NH(CH2)2—SS—(CH2)2—CO-Gly-∊ Ahx-[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group. 1H-NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd = 1 nM) and hence is a promising tool in their detection (autoradiography, gold-, ferritin-, enzyme-, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe-receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling 1 + 2 in presence of (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of the D-Phe8 derivative that has antagonist properties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720409
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  • 91
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    Synthesis of 11-Oxaestrogens via Dye-Sensitized Photo-oxygenation of a 9,11-Didehydroestrone Derivative (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 725-730 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 3-methoxy-1 1-oxaestrone (13) has been synthetized from estrone (3) following an approach that involves the ring-C fragmentation of the estrogenic skeleton by dye-sensitized photo-oxygenation of the properly C(17)-protected 9,11-didehydroestrone derivative 6 as the key step. The C(13)-side-chain degradation of the 9-oxo-9,11-seco-aldehyde 7 followed by reduction to the 9β, 12-diol 10 and further cyclization yields the 11-oxaestrogenic skeleton. By this procedure, 13 is obtained in 9 steps from 3 with a non-optimized overall yield of ca. 15%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720412
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  • 92
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    Photo-oxygenation of Styrenic Estrogens: Product characterization and kinetics of the dye-sensitized photo-oxygenation of 9,11-didehydroestrone derivativesPhotochemical Reactions, Part 23. Part 22: [1] (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 715-724 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dye-sensitized photo-oxygenation of 3-hydroxyestra-1,3,5(10), 9(11)-tetraen-17-one (8) gives a complex mixture from which only the 1,4-endo-peroxide 10 can be isolated in low yield. In contrast, the 3-methoxy derivative 9 yields the C-seco-aldehyde 11 as a major product, suggesting that 1,2-dioxetane is a primary photo-oxygenation intermediate. As the electron-donating character of the substituent at C(3) decreases in the sequence 12 (R = PhCO), 13 (R = Ac), and 14 (R = Ts), the rate constant in substrate disappearance becomes drastically smaller as compared with 8 and 9, and no photoproducts are detected. The results are rationalized by means of electronic and conformational factors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720411
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  • 93
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    Synthèse énantiospécifique des acides (+)-(2R)- et (-)-(2S)-éthyl-6-dihydro-3,4-méthyl-2-oxo-4-2H pyranecarboxylique-5 (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 731-737 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiospecific Synthesis of (+)-(2R)- and (-)-(2S)-6-Ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic AcidThe two enantiomers (-)-(2S)- and (+)-(2R)-6-ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic acid ((S)- and (R)-7) have been synthesized from (+)-(3S) and (-)-(3R)-3-hydroxybutanoates, respectively (Scheme 1). By reduction and decarboxylation, the tetrahydro-2H-pyranols (2R, 4R, 6S)- and (2S, 4S, 6R)-13, respectively, were obtained with an enantiomeric excess of ≥ 93%.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720413
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  • 94
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    Pteridines. Part XLIPart XL, see[1]. Synthesis and properties of 6,7,8-trimethyl-4-thiolumazine (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 738-743 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first representative of the 8-substituted 4-thiolumazine series has been synthesized. In a sequence of reactions, 4,6-dichloropyrimidin-2-(1H)-one (1) is first converted into 4-chloro-6-(methylamino)pyrimidin-2(1H)-one (6), then the Cl-atom displaced by the thioxo group (→7) followed by a coupling reaction with 4-chlorophenyldiazonium chloride to introduce the necessary N-function into the 5-position (→ 9; Scheme 1). Reduction of the p-chlorophenylazo group leads to the 6-(methlyamino)-4-thiouracil-5-amine (10) which on condensation with diacetyl gives 6,7,8-trimethyl-4-thiolumazine (8). The physical properties of 8 are compared with the 2-thio analog and 6,7,8-trimethyllumazine indicating that 8 possesses the highest acidity and the longest UV absorption.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720414
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    Studies on the Biosynthesis of Spirostaphylotrichin A (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 774-783 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incorporation of 14C-labelled acetate and amino acids as well as of [1-13C]-, [2-13C]-, and [1,2-13C2] acetate, L-[methyl13C] methionine, [2,3-13C2] succinate, and L-[2,3-13C2] aspartate into spirostaphylotrichin A (1) by Staphylotrichum coccosporum demonstrates that the building blocks of 1 are 5 units of acetate/malonate, 1 unit of methionine, and a C4-dicarboxylic acid. The latter is most likely aspartate and derived from the citric-acid cycle. Using [2-13C, 2-2H3] acetate as a precursor, the starter unit of the polyketide chain was identified.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720418
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    New Spirostaphylotrichins from Staphylotrichum coccosporum (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 784-792 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isolation and structure elucidation of the new spirostaphylotrichins B (2), C and D (3/4), F (5), Q (6), and R (7) are described. Compounds 2 and 3 are artefacts formed during the isolation of the metabolites from the cultures. The absolute configuration of spirostaphylotrichin A (1) has been determined by CD spectroscopy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720419
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  • 97
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    Diazotisation Mechanism of Heteroaromatic Amines. Diazotisation of 2-aminothiazole as an equilibrium (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 800-805 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate of diazotization of 2-aminothiazole was measured in 65 to 75% (w/w) aqueous H2SO4. The kinetic solvent isotope effect of the diazotization in 72% D2SO4/D2O was determined (kH/kD = 5.8 ± 0.2). These data are consistent with a mechanism in which the 2-aminothiazole, protonated at the ring N-atom, but not at the NH2 group, is attacked by the NO+ ion. The reaction does not go to completion, but to an equilibrium. The equilibrium concentration of the diazonium ion was determined in 30,50,70, and 90% (w/w) H2SO4 at three initial concentration of reagents (0.001,0.01, and 0.1m). The final concentrations of the reagents and the diazonium ion are consistent with a reversible process. This is the first diazotization for which quantitative evidence for equilibration has been found. In the very large range of acidities used (Ho = -1.73 to -9.01), it was not possible to calculate meaningful equilibrium constants that are independent of the acidity.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19890720421
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  • 98
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    Struktur/wirkung-Beziehungen bei Geruchsstoffen mit dem Bicyclo[2.2.2.]octan-GerüstHerrn Dr. Günther Ohloff mit den besten Wünschen zum 65. Geburtstag gewidmetAuszugsweise vorgetragen an ‘The Conference on Terpene Chemistry’, 25.4.1986, Grasse, und am ‘19th International Symposium on Essential Oils and Other Substrates’, 9.19.1988, Greinfensee/Dübendorf, Schweiz. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 806-810 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure-Activity Relationships of Odorants with a Bicyclo[2.2.2]octane SystemThe synthesis of the olfactory interesting homonojigikualcohol 2 and of its epimer 10 leads to the keto alcohols 6a, b and 7a, b as intermediates. The latter have OH and C=O groups (an AH/B system) fixed at the rigid bicyclic nucleus at different distances (2.8 and 4.7 Å) and confirm Ohloff's rule for odoriferous properties which is based on this distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720422
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  • 99
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    Solubilization of Peptides in Non-polar Organic Solvents by the Addition of Inorganic Salts: Facts and ImplicationsDedicated to Prof. Gerhard Schröder on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 857-867 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solubility of open-chain peptide derivatives (12 examples) in non-polar, ether-type organic solvents may be greatly increased by addition of salts (LiCl, LiBr, LiI, LiBF4, LiClO4, NaI, MgBr2 CaBr2, ZnCl2) or of titanates (Ti(OEt)4, Ti(OCHMe2)4). Examples are reported (Tables 2-6) in which this solubilizing effect leads to peptide concentrations more than one-hundred-fold those in the absence of salt (cf, Boc—Ala—Gly—Gly—Gly—OH in THF from 2g·1-1 to ≥ 300 g·1-1 with 6 equiv. of LiCl), 1H-NMR Spectra of one of these solutions are reported (Fig. 1). There are no indications for epimerizations of stereogenic centres on the peptide backbone. Possible applications of these solutions in peptide chemistry are discussed.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19890720502
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  • 100
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    Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]ironPart of the planned Ph. D. thesis of Edia Bonfantini, Ecole Polytechnique Fédérale de Lausanne. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 906-916 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene-l-methanol (7) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe2(CO)9] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene (8) led to the formation of a 1.7:1 mixture of ‘trans’ (19, 21, 22) vs. ‘cis’ (20, 23, 24) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron (25) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron (26). The structures of products 19 and of its exo (21) and endo (22) [Fe(CO)3(1,3-diene)]complexes) and 20 (and of its exo (23) and endo (24) (Fe(CO)3(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron (21). In the latter, the Fe(CO)3(1,3-diene) moiety deviates significantly from the usual local Cs symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η3-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).
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    URL: http://dx.doi.org/10.1002/hlca.19890720506
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