Library

Notes: The (12-20)-nonapeptide Z-Leu-Aib-Pro-Val-Aib-Aib-Glu (OBzl)-Gln-Pheol (10) of the ionophor alamethicin was synthesized by a new strategy, using 3-amino-2,2-dimethyl-2H-azirines 2 as synthons for the α-aminoisobutyric acid (Aib) moieties.

Notes: Controlled ozonolysis of 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane (1) afforded 3,5,6-trimethylidene-7-oxabicyclo[2.2.1]heptan-2-one (2). Ozonolysis of 2 gave a 1:1 mixture of 3,5-dimethylidene-7-oxa-bicyclo[2.2.1]heptane-2,6-dione (3) and 3,6-dimethylidene-7-oxabicyclo[2.2.1]heptane-2,5-dione (4). The He(Iα) photoelectron (PE) spectra of 2 and 4 have been recorded. Comparison with the PE data of related systems, and with the result of ab initio STO-3G calculations, confirm the existence of significant through-bond interactions between the oxygen lone-pair orbitals n(CO) of the carbonyl functions and n(O) of the O(7) ether bridge.

Notes: The 1,2,3,4,4a,5,8,8a-octahydro-4β8aα-dimethylnaphthalen-4aβ-ol (= dehydrogeosmin; 1) has been identified as the olfactorily dominant compound in the flower scents of Rebutia marsoneri WERD., Dolichothele longimamma (DC.) BR. et R., and Sulcorebutia kruegeri (CARD.) RITT. The structure of 1, which might be of importance to the pollination biology of such Cactaceae, is based on spectral data and synthesis.

Notes: The Cu2+ complex of 1, having a non-coordinating carboxylic group, can be reacted under the typical conditions of peptide formation with amines such as 2-methylpropylamine or (pyrid-2-yl)methylamine to give, after removal of Cu2+ with CN-, the amides 4 and 5. The Cu2+ ion is of paramount importance since it protects the four amino groups of the macrocycle so that the amide condensation can specifically be done with the exogenous amine It is also shown that the Cu2+ complex of 1 can be covalently attached to bovine serum albumin (BSA), thus opening the possibility to use this compound as a labelling agent for proteins and antibodies.

Notes: Base treatment of azomalonates derived from N-substituted dialkyl (2-chloroacetamido)malonates results in the formation of 4-substituted alkyl 5-oxo-1,4,5,6-tetrahydro-1,2,4-triazine-3-carboxylates. The same malonates coupled with diazotized 2-amino-5-chlorobenzophenone or methyl anthranilate afford triazinones which can be cyclized into novel triazino[1,6-a]indoles. Two representative heterocycles are further characterized by typical reactions. Whereas oxidation gives the corresponding triazine-5,6-diones, the outcome of the reduction is strongly dependent on the nature of the substituent at C(4). Bromination followed by aqueous workup leads to the 6-hydroxy derivatives. Some mechanistic aspects of this novel triazinone synthesis are discussed.

Notes: (3S,5R,6E,8E)-Deca-6,8-diene-1,3,5-triol, a New Metabolite from Streptomyces fimbriatus (MILLARD et BURR 1926)The title compound 2, a new C10-metabolite related to the previously found (3S-8E)-1,3-dihydroxydec-8-en-5-one (1), was isolated from the culture filtrate of Streptomyces fimbriatus, strain Tü 2335 by solvent extraction and chromatography. The constitution and the absolute configuration were determined by spectroscopic methods and chemical derivatization. The relative configurations were determined by NOE measurements with the silyl-protected 3,5-isopropylidene derivative of 2.

Notes: A combined computational (MO ab initio) and structural-statistical study of molecules containing the O—C—N moiety is presented. Aminomethanol, the simplest member of this series, was computed using GAUSSIAN-82 with the 3-21G and 6-31G* basis sets and with complete geometry optimization, as well as with MP3//6-31G*. A set of carefully selected molecules containing the O—C—N unit was retrieved from the Cambridge Structural Database (CSD), and its structural parameters were analyzed according to an established procedure. Comparison between experimental and computational data was thus made possible. Results are consistent with the co-existence of two unequal anomeric effects in this system: a strong nN-σ*C—O anomeric interaction, and a weak nπO-σ*C—N one. The ability of the two basis sets to reproduce the energies and structural characteristics of the stereoelectronic effects is assessed, including the significance of using polarization functions and the inclusion of correlation energy.

Notes: F430M, the pentamethyl ester of coenzyme F430, can be oxidized reversibly by one electron. The oxidation potential has been determined, and the electrolytically prepared oxidation product was characterized by its UV/VIS and ESR spectrum. The strongly anisotropic and nearly axial ESR spectrum is consistent with a S = ½ species with the unpaired-electron spin density predominantly in a dz2-type orbital of the central nickel ion. The properties of Ni(III)F430M are discussed in the context of two hypothetical mechanisms for the catalytic role of coenzyme F430 in methyl coenzyme M reductase, which catalyses the last step of methane formation in methanogenic bacteria.

Notes: The η2-acyl complex [Fe(η2-EtC=O)I (CO)(PEt3)2] (1a) reacts with phenylacetylene in refluxing Et2O to form a mixture of products including [Fe(C(Ph)=CHC(O)Et}I(CO)(PEt3)2] (3), [Fe{C(Ph)=CHC(O)Et}1(CO)2(PEt3)2] (4), and [Fe{C(=CHPh)C(O)Et)I(CO)(PEt3)2] (5). Compound 3 contains a ‘metallafurane’ unit, while 5 consists of a 4-member metallacycle. Compound 5 was characterized by X-ray crystallography. In contrast to 1a, the η2-acyl complex [Fe{η2-(i-Pr)CO}I(CO)(PEt3)2] (1b) reacts with phenylacetylene under similar conditions to produce [Fe{η2-C(O)C(Ph)=CH(i-Pr)}I(CO)(PEt3)2 (7) which was characterized spectroscopically. Modified extended Hückel theory calculations were made on the model compounds [Fe(η2-CHO)(CO)2(PH3)2]+ (14), [Fe(CHO)(HCCH)(CO)2(PH3)2]+ (15), [Fe(=C=CH2)(CHO)(CO)2(PH3)2]+ (16), [Fe{C(=CH2)CHO}(CO)2(PH3)2]+ (17), and {Fe(CH=CHCHO)(CO)2(PH3)2]+ (18). The calculations show that in the transformation 15→18, there exists a transition state lying 83.6 kJ/mol above the optimized geometry of 15 in which the formyl unit is rotated by 80° with respect to the Fe-acetylene plane. Conversion of 15 to 17 involves a [1,2]-H shift and an acyl-acetylene coupling reaction which probably occur synchronously.

Notes: The preparation of complexes [MX2(1)] (M = Ni, Pd, and Pi; X - Cl, Br, and I; 1 = 1,2-bis[(diphenylphosphino)methyl]benzene). [Pt(OSO2CH3)Et(1)], [Pt(alkene)(1)] (alkene - C2H2, and CH2 = CHCN), and [(1)Pt-(μ-H)2PtH(1)][BPh4] is reported. Their 1H- and 31P-NMR spectra were recorded and used lor structural assignments. The X-ray crystal structure of [Pt(C2H4)(1)] was determined. It is shown that the P—Pt—P bond angle in this complex differs significantly from those found in related compounds with monodentate phosphines, and that this difference is likely to be due to intramolecular contacts.

Notes: As a direct test of the Cane-Westley hypothesis concerning the mode of assembly of ether rings in the polyether class of ionophore antibiotics, we describe experiments culminating in the synthesis of three putative intermediates on the monensin biosynthetic pathway and incorporation experiments with these materials and the monensin-producing organism Streptomyces cinnamonensis. The putative intermediates synthesised include the trienes [21-3H]-7 and [13-3H]-10, and the diene [9-3H]-11. The results of the incorporation experiments conducted with whole cell cultures suggest that [13-3H]-10 and [21-3H]-7 are unable to cross the intact cell membrane of S. cinnamonensis, whereas diene [9-3H]-11 can gain entry to the cellular interior, but is then degraded efficiently, most likely by a pathway closely related to β-oxidation, without being specifically incorporated into the antibiotic.

Notes: The platinum(0) complexes [Pt(C2H4)(PP)] (PP = 1,2-bis[(diphenylphosphino)methyl]benzene (2) and (+)-DIOP = (+)-1,4-bis(diphenylphosphino)-1,4-dideoxy-2,3-O-isopropyliden-D-threitol), when promoted by CH3SO3H, become active catalysts for styrene hydroformylation with total yields of aldehydes ranging from 44 to 67% und selectivities towards 3-phenylpropanal ranging from 80 to 88%. Smaller amounts of the corresponding alcohols (3-18%) are also obtained with a selectivity towards 3-phenylpropanol of 94-96%. When DIOP complexes were used, no stereoselectivity for asymmetric hydroformylation was observed.

Notes: The synthesis of 8-aza-1,3-dideaza-2′-deoxyadenosine (3a) as well as of 4- and 5,6-substituted benzotriazole 2′-deoxy-β-D-ribonucleosides is described (Schemes 1-3). Glycosylation of benzotriazole anions is stereoselective in all cases (exclusive β-D-anomer formation), but regioisomeric N1, N2, and N3-(2′-deoxyribofuranosides) are formed. The distribution of the regioisomers is controlled by the nucleobase substituents. Anomeric configuration as well as the position of glycosylation are determined by UV and NMR in combination with 1D-NOE-difference spectroscopy. The unprotonated forms of 4-aminobenzotriazoic 2′-deoxy-β-D-ribofuranosides 3a-c exhibit strong fluorescence.

Notes: Regiospecific Synthesis of (Polyhydroxypropyl)-pterins: Synthesis of D-Anapterin and L-PrimapterinCondensation of 2,5,6-triaminopyrimidin-4-one(5) with the semicarbazone of pentoses proceeds regiospecifically with formation of 7-(polyhydroxypropyl)pterins. D-Anapterin (=7-(D-erythro-1′,2′,3′-trihydroxypropyl)pterin; D-3) was obtained in 40% yield, and L-primapterin (=7-(L-erythro-1′,2′-dihydroxypropyl)pterin; L-4)in 10% yield.

Notes: Halochromic Molecules. Substituted 6,11-Dihydrospiro[[1]benzopyrano[4,3-b]indol-6,9′-9′H-xanthene]-2′,6′-diamines and Their Aza Analogues: New Chromogenes for Black Images.We have synthesized a series of substituted 6,11-dihydrospiro[[1]benzopyrano[4,3-b]indo1-6,9′-9′H-xanthene]-2′,6′-diamines and their respective aza analogues. These compounds develop a black colour in acidic media. The assumed structures of the analytically pure starting and final products are consistant with the fragmentations in the MS and are also supported by FT 1H-NMR. The UV/VIS spectra in buffered MeOH/H2O solutions were measured. From the ∊pH* curves, we determined the pK* values. The title compounds can be used in so-called pressure-sensitive copying systems.

Notes: Reaction of 3-(Dimethylamino)-2H-azirines with 1,3-Oxazolidine-2-thione to 3-(2-Hydroxyethyl)-2- thiohydantoinsThe reaction of 3-(dimethylamino)-2H-azirines 1 and 1,3-oxazolidine-2-thione (6), in MeCN at room temperature, yields, after hydrolytic workup, 3-(2-hydroxyethyl)-2-thiohydantoins 7 (Scheme 2). In the case of the spirocyclic 1c, crystallization of the crude reaction mixture leads to spiro [cyclopentane-1, 7′(7′aH)-imidazo [4, 3-b] oxazole] -5′-thione 8c. The mechanism is discussed.

Notes: Reaction of 3-(Dimethylamino)-2H-azirines with 1,3-Benzoxazole-2(3H)-thioneThe reaction of 3-(dimethylamino)-2H-azirines 2 with 1,3-benzoxazole-2(3H)-thione (5), which can be considered as NH-acidic heterocycle (pKaca. 7.3), in MeCN at room temperature, leads to 3-(2-hydroxyphenyl)-2-thiohydantoins 6 and thiourea derivatives of type 7 (Scheme 2). A reaction mechanism for the formation of the products via the crucial zwitterionic intermediate A′ is suggested. This intermediate was trapped by methylation with Mel and hydrolysis to give 9 (Scheme 4). Under normal reaction conditions, A′ undergoes a ring opening to B which is hydrolyzed during workup to yield 6 or rearranges to give the thiourea 7. A reasonable intermediate of the latter transformation is the isothiocyanate E (Scheme 3) which also could be trapped by morpholine. In i-PrOH at 55-65° 2a and 5 react to yield a mixture of 6a, 2-(isopropylthio)-1,3-benzoxazole (12), and the thioamide 13 (Scheme 5). A mechanism for the surprising alkylation of 5 via the intermediate 2-amino-2-alkoxyaziridine Fis proposed. Again via an aziridine, e.g. H (Scheme 6), the formation of 13 can be explained.

Notes: The [4 + 2] cycloaddition stereoselectivity of dienamines 1-4 with dimethyl fumarate and fumaronitrile has been investigated, and functionalised decalins 21-40 have been prepared by elimination of Me2NH from cycloadducts 7-11 and 15-20; in the context of the synthesis of drimane sesquiterpenes, the reduction of dienediesters 29 and 30 is also described.

Notes: Preparations of dimethyl (1RS,2SR,4RS,5SR,6SR,7RS)- and dimethyl (1 RS,2SR,4RS,5SR,6RS,7SR)-8-oxa-3-azatricyclo[3;2.1.024] octane-6,7-dicarboxylate 15 and18, resp.) and of their N-(tert-butyloxy)carbonyl (14, 17) and V-benzoyl (16, 19) derivatives are described. While treatment with nucleophilic acids (HCl, HBr. AcOH) of the exo, exo-diesters 14 and 16 gave the corresponding products 23-27 of aziridine trans -addition, the exo, endo -diesters 17 and 19 led to the corresponding amino-lactones 63 (methyl (1RS,2RS,3SR,6RS,7SR,9RS)-2-{[(tert-butyloxy)carbonyl] amino}-5-oxo-4,8-dioxatricyclo[4.2.1.0 37] nonane-9-carboxylate) and 64 (methyl (1RS,2RS,3SR,6RS,7SR,9SR)-2-(benzoylamino)-5-oxo-4,8-dioxatricyclo[4.2.1.0 3′7] (nonane-9-carboxylate). Under non-nucleophilic acidic conditions, the N-benzoylaziridine 16 was rearranged quantitatively into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)-4-phenyl-5,10-dioxa-3-azatricyclo[4.3.1.02′7] dec-3-ene-8,9-dicarboxylate(31), and 19 into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)-4-phenyl-3,10-dioxa-5-azatricyclo [5.2.1.02′6] dec-4-ene-8,9-di-carboxylate (65). Possible mechanisms of these highly selective reactions and rearrangements are discussed.

Notes: Ozonolysis of the easily available monoterpenoids (-)-1 and (+)-1 leads in high yield to the ketoaldehydes (-)-4 and (+)-4, which serve as convenient intermediates for efficient new routes to both optical antipodes of the naturally occurring octenediol (E)-2 (Monarch butterfly secretion product) and octene-dicarboxylic acid (E)-3 (Callosobruchus chinensis sex pheromone). All steps proceed with almost complete retention of configuration, ensuring the synthesis of the target compounds with high optical purity.

Notes: Novel tricyclic heterocycles were prepared and evaluated for their affinity to the central benzodiazepine receptor. The most potent compounds with IC50's in the nanomolar range were; found among thienoquinolizines and benzo[a]quinolizines (cf. Tables 2-5). The central ring of the tricyclic ring system may be partially unsaturated (cf. Tables 2 and 4) or fully unsaturated (cf. Tables 3 and 5) without loss of the high affinity to the receptor. The position of the ester group in the pyridinone ring is crucial for good binding (cf. Tables 1 and 2). It may be replaced by a broad variety of functional groups, e.g. amides, alkyl carbamates, alkyl groups, and hydroxyalkyl groups (cf. Tables 2-5). In the benzo[a]quinolizines, shifting the halogen atom from C(10) to C(9) leads to complete loss of affinity to the benzodiazepine receptor (cf. Table 4).

Notes: Synthesis of 2,4-Diamino-thieno[2,3-d]pyrimidinesCondensation of 2-aminothiophene-3-carbonitrile (4) with guanidine or sequential addition of CS2 and NH3 to 4 provides 2,4-diaminothieno[2,3-d]pyrimidine (7). This compound yields, after sequential addition of sec-BuLi and either [3-(trifluoromethyl)benzene]sulfenyl chloride (8) or the corresponding disulfide 9, followed by acidic work up, 2,4-diamino-6-{[3-(trifluoromethyl)phenyl]thio}thieno[2,3-d]pyrimidine (10). In another approach, 2-amino-5-{[3-(trifluoromethyl)phenyl]thio}thiophene-3-carbonitrile (11) obtained from 4 and 8 is transformed to 10 by condensation with guanidine. Corresponding to the second route, 2,4-diamino-6-[(naphth-2-yl)thio]thieno-[2,3-d]pyrimidine (16) is synthesized. Oxidation of 10 with m-chloroperbenzoic acid gives 2,4-diamino-6-{[3-(tri-fluoromethyl)phenyl]sulfinyl}thieno[2,3-d]pyrimidine (13).

Notes: Pteridines: Synthesis and Characteristics of 5,6-Dihydro-6-(1,2,3-trihydroxypropyl)pteridines: Covalent Intramolecular AdductsVarious 5,6-diaminopyrimidines (1, 15, 24, 33) were condensed with the phenylhydrazones of L-(2) and D-arabinose (3) in acidic medium under N2 to give formal 5,6-dihydro-6-(1,2,3-trihydroxypropyl)pteridines (see, e.g., 4 and 5), the latter turned out to exist preferentially as intramolecular adducts, the hexahydropyrano-[3,2-g]pteridines 6, 7, 16, 17, 25, 26, and 34, formed subsequently by addition of the terminal OH group of the side-chain to the C(7)=N(8) bond of the pteridine moiety. Spectroscopically, the isomeric hexahydrofuro-[3,2-g]pteridines 10,11,18,19, and 35 were also detected as minor components in the equilibrium mixtures. In the 4-amino-2-(methylthio)pteridine series, crystallization of 6 and 7 led to the stereochemically pure (3S,4R,4aR, 10aS)-6-amino-3,4,4a,5,10,10a-hexahydro-8-(methylthio)-2H-pyrano[3,2-g]pteridine-3,4-diol (8) and its corresponding enantiomer 9, respectively Structure 8 was proven by X-ray analysis. Acylation of the hexahydropyrano[3,2-g]pteridines yielded the more stable tri-, tetra-, and pentaacetyl derivatives 12-14, 20-23, 27-32, and 37-39 which were characterized and of which the absolute and relative configurations were determined (1H- and 13C-NMR and UV spectra, chiroptical measurements, elemental analyses).

Notes: Starting from the readily available, optically active (4R)-4-hydroxy-2,2,6-trimethylcyclohexanone (1), a new technical synthesis of (3R,3′R)-zeaxanthin is described. According to a 2(C9 + C6) + C10 = C40 construction scheme, the ketone 1 was first transformed with (E)-3-methylpent-2-en-4-yn-1-ol (5) into a C15-intermediate which, by a three-step sequence, could be converted into the known olefinic C15-Wittig salt 4. Optimized conditions for the final Wittig reaction of 4 with the C10-dialdehyde 3 are discussed. Based on 1, the overall yield of the entire technical process is ca. 40%.

Notes: Two new 20(10→5)abeo-abietune diterpenoids, pygmaeooins B (1) and C (2), have been isolated from the roots of Pygmaeopremna herbacea (Verbenaceae). Their structures were elucidated on the basis of spectroscopic data, and chemically, both compounds were correlated with each other. The absolute configurations were assigned tentatively on the basis of biogenetic pathway.

Notes: The 12H-dibenzo [d, g] dioxathiocines 2 and 4 are prepared by condensation of the corresponding bis[phenols] 1 and 3 with SOCl2 and SCl2, respectively. X-Ray analysis reveals the presence of the boat-chair (BC) form as the only conformer in the solid state of the cyclic thiodioxy derivative 4a, whereas the sulfinyldioxy compound 2a exists in the asymmetric axial boat (B) form, i. e. with endo (axial) orientation of the exocyclic O-atom. Conformational analysis using 1H-NMR spectroscopy indicates the presence of a boat form for compounds 2, whereas compounds 4 again exist in the boat chair form. A comparison of 1H-NMR and thermodynamic parameters with those of the cyclic sulfinyldioxy compound 5 with an equilibrium between e-BC and a-BC form (i.e. BC form with equatorial and axial orientation of the exocyclic O-atom) is made.

Notes: The hydrogenations of methyl 2-oxoeyclopentanecarboxylate (1), ethyl 2-oxocyelohexanecarboxylate (3), and 2-methylcyclohexanone (5) on unmodified Raney-Ni catalyst lead predominately to the formation of the cis-hydroxy diastereoisomers of 2, 4, and 6, respectively (Scheme 2). In the asymmetric hydrogenations on catalysts modified with chiral tartaric acid ((R, R )-C4H6O6/Raney-Ni and (R, R)-C4H6O6/NaBr/Raney-Ni), the predominance of the cis-isomer increases significantly. The hydrogenations of β-keto esters 1 and 3 proceed with an enantioselectivity of 10-15% on the modified catalysts, while the similar hydrogenation of 5 yields optically inactive 6. The (1S,2R)-enantiomers of the cis-isomers of 2 and 4 are formed in larger quantity, whereas the (lR,2R)-enantiomers of the corresponding trans-isomers predominate (Scheme 1). The enantioselective formation of trans-2 and trans-4 can be interpreted mainly in terms of the asymmetric hydrogenation of cyclic β-keto esters through the keto form, while that of the corresponding cis-hydroxy esters proceeds through the enol form.

Notes: Chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-O-yl)titanium (1) is used for the transmetallation of Li-enolates obtained from propionyl derivatives. While such Ti-enolates of ketones and hydrazones appear to be unreactive, the (E)enolate 13 of 2,6-dimethylphenyl propionate (11) adds to the re-side of aldehydes, affording various syn-aldols 14 with high dia- and enantioselectivity (92-97% ds, 91-97% ee, cf. Scheme 2 and Table 1). Racemic syn-aldols (±)-14 are obtained analogously from the achiral bis(2-propyloxy)-Ti-enolate 15 (Scheme 2 and Table 2). In contrast to the unstable Li-enolate 10, the Ti-enolates 13 and 15 isomerize at -30°, presumably to the thermodynamically more stable (Z)-enolates (Scheme 4), While the diastereoselectivity of the achiral enolate 15 is lost upon this equilibration, the chiral (Z)-enolate 27 quite unexpectedly affords anti-aldols 12 of high optical purity (94-98% ec) and, in most cases, with acceptable-to-good diastereoselectivity (82-90% ds). Notable exceptions are branched unsaturated and aromatic aldehydes which form a greater proportion of synepimers of moderate optical purity (Scheme 5 and Table 3). Consistent with these findings, re-facial-and ami -selective aldol-addition is also exhibited by the (Z)-configurated Ti-enolate 22 of N-propionyl-oxazolidi-none 19 (Scheme 3).

Notes: Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related CompoundsStarting from our previously described synthon 1, the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4-(2′,4′-dihydroxy-2′,6′,6′-trimethylcyclohexylidene)but-3-en-2-ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.

Notes: Novel cationic allylpalladium (II) comp, exes containing the alkaloid (-)sparteine (1) as a bidentate ligand have been prepared. Two of them, [η3(cyclohex-2-enyl)] (sparteine)palladium(II) hexafluorophosphate([Pd(η3-C6 H9)(sparteine)][PF6] 3b) and (sparteine)[η3-(1,1,3-triphenylallyl)] palladium (II) trifluorophosphate ([Pd(η3-Ph2CCHCHPh)(sparteine)][sparteine)] [CF3SO3]; (3c) were characterized by X-ray diffraction. The application of 2D-NMR methods (COSY and NOESY)affords a correlation between the solid-state and solution structures for complex 3c.

Notes: Chiral [2H] -labelled methylene groups flanked by two double bonds within (poly)unsaturated fatty acids are readily available from trans-2,3-epoxy[2,3-2H2] alk-4-yn-l-ols, obtained in their turn by asymmetric epoxidation of the corresponding (E)-[2,3-2H2] alk-2-en-4-yn-l-ols (see Scheme 3). The procedure is exemplified for (8S,3Z,6Z,9Z)-[7,8-2H2] trideca-3,6,9-trienoic acid ((8S)-11) and (8R)-11 (Scheme 4) as well as for (5S,3Z,6Z)-[4,5-2H2]deca-3,6-dienoic acid ((5S)-13) and (5R)-13 (Scheme 5).

Notes: Separation and Quantitation of All Eight Stereoisomers of α-Tocopherol by ChromatographyThe results of the analysis of several derivatives of (all-rac)-α-tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl-ether derivative allows the separation and quantification of all eight possible stereoisomers of (all-rac)-α-tocopherol.

Notes: The Mediterranean alcyonacean Alcyonium ( = Parerythropodium) coralloides (Pallas, 1766) is shown here to contain coralloidolide F ( = (+)-(3a-R*, 7R*, 8R*, 9R*, 12R*, 12aS*)-8,9-epoxy-1,3a,6,7,8,9,10,11,12,12a-decahydro-3a-hydroxy-12-isopropenyl-2,5-dimethyl-1-oxocyclopfintacycloundecene-9,7-carbolactone; (+)-2), the first example of a 2,6-cyclized cembranolide. Structural assignments are mainly based on ID and 2D NMR and MS data.

Notes: Cyclohex-2-enones 1a-1c undergo photocycloaddition to tetramethoxyethylene in benzene to afford 1-oxa-spiro[3.5]non-5-enes 3 in very good yields. In MeCN as solvent, higher relative amounts of bicyclo[4.2.0]octan-2-ones 4 are formed. Results from similar experiments with the same enones and 2,3-dimethylbut-2-ene or 1,1-dimethoxyethene indicate that the driving force for oxetane formation is a sufficiently large difference in redox potentials between Ered of the enone and Eox of the alkene. A mechanism is proposed for cycloalk-2-enone + alkene photocycloadditions wherein the cyclobutane adducts arise from an exciplex intermediate and the oxetanes from a subsequently formed contact ion-pair.

Notes: The Synthesis of Some 2H-Pyran-2-one DerivativesDerivatives of 6-unsubstituted 2H-pyran-2-one have been synthesized by several different methods. The 4-chloro-2H-pyran-2-one (9) is the most important, since it serves as starting material for the synthesis of different 4-substituted 2H-pyran-2-ones (Scheme 2). Also described are simple transformations of cumalic-acid derivatives producing 5-(2,2-dichlorovinyl)-2H-pyran-2-one (23), 2-oxo-2H-pyran-2-carbonitrile (26), and 4,5-bis(trifluoromethyl)-2H-pyran-2-one (32) (Scheme 3 and 4).

Notes: (±)-Muscone ((±)-1) has been synthesised in three steps from 2-(2′-methylprop-2′-enyl)cyclododecan-1-one (2). The synthesis involves two key transformations: a Lewis-acid-mediated intramolecular ene reaction (2→3) and the β-cleavage of the bicyclic potassium alkoxide 3a′ to the macrocyclic enone (Z)-11.

Notes: The thermal and hydrolytic degradation of tetrahydrolipstatin (THL, 1) was investigated. All main degradation products were isolated, characterized, and synthesized. Labile intermediates unavailable to isolation were detected and identified by GC/MS analysis of their silylated derivatives, and whenever possible, compared with independently prepared reference compounds. The identified degradation products represent at least 97% of the total degradation mixture. Two main reaction pathways arc proposed. Pharmacological data are reported for the degradation mixture and the main degradation products.

Notes: Natural primapterin (80 μg) was isolated from 200 ml of urine of a patient with mild hyperphenylalaninemia. The CD curve of the compound showed that it belongs to the L-series of 7-(polyhydroxypropyl)pterins.

Notes: A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl CompoundsA new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)-L-diisopropyl-tartrate acetals derived from dihydrocitronellal (6), hexahydropseudoionone (3), hexahydrofarnesal (7), and hexahydro far nesy lace tone (4), the C10, C13, C15, and C18 intermediates in various syntheses of naturally occurring tocopherols and vitamin K1, can be achieved by capillary GC on a cyanopropylsilicon-coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present-day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C-atoms bearing two stereogenic centres is performed in a single operation for the first time.

Notes: Synthetic procedures have been developed for the preparation of ligands bearing two to six pendent, unsubstituted or substituted 2, 2′-bipyridine groups attached to acyclic (tripode, tetrapode) and macrocyclic (triazanonade-cane, cyclam, hexacyclen, bis(bipyrido)hexaazamacrocycle) polyamines. Ligands 1-5 have been obtained in high yield by condensation of 6-(bromomethyl)-2, 2′-bipyridine (9b) with the corresponding amines in the presence of NaOH, H2O, and MeOH. Ligands 6-8 have been prepared in good yield by condensation of 9b or the di- or tetrasubstituted mono (bromomethyl) bipyridine 10b or 11b, respectively, with the corresponding amines in the presence of Na2CO3 and MeCN. Ligand 1 forms hemi-cage complexes with RuII, FeI, CrII, and CrIII cations and trinuclear complexes with [RuCl2(bpy)2] and [ReCl(CO)5]. Tetrapode 2 and hexapode 4 gave tetranuclear and dinuclear complexes, respectively, by reaction with Fe11 salts. These complexes possess a variety of interesting physical and chemical properties.

Notes: The recently developed general principle of ion-selective optode membranes, based on conventional ionophores, was employed to design a new approach to the determination of enantiomeric excess. Highly lipophilic chiral crown derivatives, exhibiting a high selectivity for a chiral ammonium guest cation, are combined with a H+-selective chromoionophore in a plasticized PVC membrane. The enantiomer recognition process is translated by this sensor with an optical transduction into a signal easily measured by a conventional spectrophotometer, and enantiomeric excess can be determined without the need for polarized light. Characteristics and a theoretical description of these new optode membranes are given.

Notes: ‘tert-Amino Effect’ on Acidic Treatment of (Pyrrolidin-l-yl)azadienesThe behaviour of 4-morpholino- and 4-(pyrrolidin-l-yl)-2-aza-1. 3-diene-l, l-dicarbonitriles 3, and 4 and 10, respectively, in acidic medium is described. The former gives with HBr/AcOH 3-bromopyrazine-2-carbonitrile 6. On the other hand, pyrrolidin-1-yl derivatives 4 and 10 furnish, by a [1, 5]-H shift, pyrrolo[l, 2]pyrazine structures 5 and 11, respectively.

Notes: The convergent syntheses of 3-deazapurine 2′-deoxy-β-D-ribonucleosides and 2′,3′-dideoxy-D-ribonucleosides, including 3-deaza-2′-deoxyadenosine (1a) and 3-deaza-2′,3′-dideoxyadenosine (1b) is described. The 4-chloro-lH-imidazo[4,5-c]pyridinyl anion derived from 5 was reacted with either 2′-deoxyhalogenose 6 or 2′,3′-dideoxyhalogenose 10 yielding two regioisomeric (N1 and N3) glycosylation products. They were deprotected and converted into 4-substituted imidazo[4,5-c]pyridine 2′-deoxy-β-D-ribonucleosides and 2′,3′-dideoxy-D-ribonucleosides. Compounds 1a and 1b proved to be more stable against proton-catalyzed N-glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase.

Notes: The acid-catalyzed rearrangement of N-(1′,1′-dimethylprop-2′-ynyl)-, N-(1′-methylprop-2′-ynyl)-, and N-(1′-arylprop-2′-ynyl)-2,6-, 2,4,6-, 2,3,5,6-, and 2,3,4,5,6-substituted anilines in mixtures of 1N aqueous H2SO4 and ROH such as EtOH, PrOH, BuOH etc., or in CDCl3 or CCl4 in the presence of 4 to 9 mol-equiv. trifluoroacetic acid (TFA)has been investigated (cf. Scheme 12-25 and Tables 6 and 7). The rearrangement of N-(3′-X-1′,1′-dimethyl-prop-2′-ynyl)-2,6- and 2,4,6-trimethylanilines (X = Cl, Br, I) in CDCl3/TFA occurs already at 20° with τ1/2 of ca. 1 to 5 h to yield the corresponding 6-(1-X-3′-methylbuta-1,2′-dienyl)-2,6-dimethyl- or 2,4,6-trimethylcyclohexa-2,4-dien-1-iminium ions (cf. Scheme 13 and Footnotes 26 and 34) When the 4 position is not substituted, a consecutive [3,3]-sigmatropic rearrangement takes place to yield 2,6-dimethyl-4-(3′-X-1′,1′-dimethylprop-2′-ynyl)anilines (cf. Footnotes 26 and 34). A comparable behavior is exhibited by N-(3′-chloro-1′-phenylprop-2′-ynyl)-2,6-dimethylaniline (45., cf. Table 7). The acid-catalyzed rearrangement of the anilines with a Cl substituent at C(3′) in 1N aqueous H2SO4/ROH at 85-95°, in addition, leads to the formation of 7-chlorotricyclo[3.2.1.02,7]oct-3-en-8-ones as the result of an intramolecular Diels-Alder reaction of the primarily formed iminium ions followed by hydrolysis of the iminium function (or vice versa; cf. Schemes 13,23, and 25 as well as Table 7). When there is no X substituent at C(1′) of the iminium-ion intermediate, a [1,2]-sigmatropic shift of the allenyl moiety at C(6) occurs in competition to the [3,3]-sigmatropic rearrangement to yield the corresponding 3-allenyl-substituted anilines (cf. Schemes 12,14-18, and 20 as well as Tables 6 and 7). The rearrangement of (-)-(S)-N-(1′-phenylprop-2′-ynyl)-2,6-dimethylaniline ((-)-38; cf. Table 7) in a mixture of 1N H2SO4/PrOH at 86° leads to the formation of (-)-(R)-3-(3′-phenylpropa-1′,2′-dienyl)-2,6-dimethylaniline ((-)-91), (+)-(E)- and (-)-(Z)-6-benzylidene-1,5-dimethyltricyclo[3.2.1.02′7]oct-3-en-8-one ((+)-(E)- and (-)-(Z)-92, respectively), and (-)-(S)-2,6-dimethyl-4-( 1′-phenylprop-2′-ynyl)aniline((-)-93). Recovered starting material (10%) showed a loss of 18% of its original optical purity. On the other hand, (+)-(E)- and (-)-(Z)-92 showed the same optical purity as (minus;)-38, as expected for intramolecular concerted processes. The CD of (+)-(E)- and (-)-(Z)-92 clearly showed that their tricyclic skeletons possess enantiomorphic structures (cf. Fig. 1). Similar results were obtained from the acid-catalyzed rearrangement of (-)-(S)-N-(3′-chloro-1′phenylprop-2′-ynyl)-2,6-dimethylaniline ((-)-45; cf. Table 7). The recovered starting material exhibited in this case a loss of 48% of its original optical purity, showing that the Cl substituent favors the heterolytic cleavage of the N-C(1′) bond in (-)-45. A still higher degree (78%) of loss of optical activity of the starting aniline was observed in the acid-catalyzed rearrangement of (-)-(S)-2,6-dimethyl-N-[1′-(p-tolyl)prop-2′-ynyl]aniline ((-)-42; cf. Scheme 25). N-[1′-(p-anisyl)prop-2-ynyl]-2,4,6-trimethylaniline(43; cf. Scheme 25) underwent no acid-catalyzed [3,3]-sigmatropic rearrangement at all. The acid-catalyzed rearrangement of N-(1′,1′-dimethylprop-2′-ynyl)aniline (25; cf. Scheme 10) in 1N H2SO4/BuOH at 100° led to no product formation due to the sensitivity of the expected product 53 against the reaction conditions. On the other hand, the acid-catalyzed rearrangement of the corresponding 3′-Cl derivative at 130° in aqueous H2SO4 in ethylene glycol led to the formation of 1,2,3,4-tetrahydro-2,2-dimethylquinolin-4-on (54; cf. Scheme 10), the hydrolysis product of the expected 4-chloro-1,2-dihydro-2,2-dimethylquinoline (56). Similarly, the acid-catalyzed rearrangement of N-(3′-bromo-1′-methylprop-2′-ynyl)-2,6-diisopropylaniline (37; cf. Scheme 21) yielded, by loss of one i-Pr group, 1,2,3,4-tetrahydro-8-isopropyl-2-methylquinolin-4-one (59).

Notes: Fluorescence measurements have been used to follow the build-up of photoproducts during the direct and benzophenone-sensitized irradiation of the title compounds 1-IN, 1-BrN, and 1-ClN (HN = naphthalene). Compounds 1-IN and 1-BrN react by homolytic dissociation through their lowest triplet and singlet excited states, respectively. Compound 1-ClN does not undergo C-Cl bond fission, except through electron transfer in the presence of an amine A, In the absence of this electron transfer, 1-ClN reacts only through substitution and oxidation processes.

Notes: Thermolysis of Heterocyclic Azidinium TetrafluoroboratesThe thermolysis of some azidinium salts was investigated. It led to a large variety of products which were isolated or identified by GC/MS. Reaction mechanisms are discussed to explain the product formation.

Notes: Reduction of indolin-2-ones with lithium aluminium hydride (LAH) or diisobutylaluminum hydride (DIBAL) and desulfurization of indoline-2-thiones with Raney-Ni were investigated. Treatment of indoline-2-ones 1 with LAH or DIBAL yield indoles 4 and/or indolines 3 in moderate-to high yield depending on the substituents at N and C(3) of 1. Indoline-2-thiones 2 were desulfurized with Raney-Ni to give indoles 4 and/or indolines 3.

Notes: 14-Methoxymetopon (= 5,14-O-dimethyloxymorphone; 4)and 14-ethoxymetopon (5) were synthesized from 14-hydroxy-5-methylcodeinone (6). In the AcOH-writhing test in mice, compound 4 was found to be ca. 20000 times more potent than morphine.

Notes: A new versatile and efficient regio-, diastereo-, and enantioselective synthesis of vicinal diols s-trans-4, s-trans-5, and s-cis-4 is described. Symmetrical ketones are converted into their SAMP-or RAMP-hydrazones which are then silylated with (isopropyloxy)dimethylsilyl chloride, followed by ozonolysis to afford the α-silyl ketones (R)-2 of high enantiomeric purity (ee 90- ≥ 98%). On the other hand, methyl ketones, after conversion into the corresponding (-)-(S)-1-amino-2-(methoxymethyl) pyrrolidine (SAMP) hydrazones, are silylated and then alkylated with RI to afford unsymmetrical α-silyl ketones (S)-3 of high enantiomeric purity (ee 90- ≥ 98%). The reduction of the above obtained α-silyl ketones with L-Selectride, followed by oxidative cleavage of the C—Si bond gives rise to s-trans-4, s-trans-5, and s-cis-4 with high diastereoselectivity (de 95- ≥ 98%) and without racemization (ee ≥ 90- ≥ 98%).

Notes: The absolute configuration of the 2-(phenylmethyl)pyridine derivatives 1-9 had been established by X-ray diffraction and chemical correlation. Their CD spectra have been studied in different solvents for the free and protonated forms. It has now been found that, from the sign of the strong CD couplet between 270 and 220 nm, which was observable for all these compounds besides 7 and 9, their absolute configuration can be determined much quicker.

Notes: Further Contributions to the Synthesis of (+)-AspicilinThere are two reasons to try to find out. whether the initial and final parts of the ‘photochemical synthesis’ of the 18-membered lichen macrolide (+)-aspicilin (5a) can be improved (cf. Schemes 1 and 2). This synthesis acts as an indicator for the utility of the earlier introduced photolactonization and as a source of large-ring-sized lactones, objects for computer-assisted conformational analysis.

Notes: Continuing studies of the global extracts from cultures of the marine deuteromycete Dendryphiella salina have led to the isolation of novel compounds that add to the scarce list of marine fungal metabolites. Besides (22E)-ergosta-4.6,8(14),22-tetraen-3-one which, though known from basidiomycetes, was unknown in the sea, they are an unusual glyceryl ester, i.e. glycer-1-yl dendryphiellale A (= (+)-(2R)-2,3-dihydroxyprop-l-yl (6S,2E,4E)6-methylocta-2,4-dienoate; (+)-1), a trinor-eremophilane, i.e. dendryphiellin A1 ( = (+)-(3R*,4E,6E)-7-{[(1R*,2S*,7R*,8aR*)-1,2,6,7,8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2yl]oxycarbonyl}-3-methylhepta-4,6-dienoic acid; (+)-11), and two eremophilanes, i.e. dendryphiellin El ( = (+)-(1R*, 2S*, 7S*,8aR*)-1,2,6,7,8,8a-hexahydro-1,8a-dimethyl-7-(1-methylethenyl)-6-oxonaphthalen-2-yl(6S,2E,4E)-6-methyl-octa-2,4-dienoate; (+)-13) and dendryphiellin E2 ( = (+)-(1R*, 2S*, 8aR*)-1,2,6,7,8,8a-hexahydro-7-isopropyl-idene-1,8a-dimethyl-6-oxonaphthalen-2-yl (6S,2E,4E)-6-Methylocta-2,4-dienoate; (+)-14). Absolute configurations have been established for (+)-1 via total synthesis and for the acid portion of (+)-13 and (+)-14 via transesterification in NaOMe/MeOH which gave in both cases melhyl dendryphiellate A ((+)-16) of known configuration and the free alcoholic moiety of (+)-14, i.e. (+)-17.

Notes: Stereoselective Syntheses of Substituted Tricarbonyl[tris(methylen)methan]iron(0) ComplexesThe complexes 3, 9, 10, 22, and 23 with one, two, and three Me substituents at the tris(methylen)methane moiety have been synthesized from the (acyloxy-1,3-diene)(tricarbonyl)iron(0) complexes 1, 4, 5, 20, and 21, respectively, by ionic hydrogenation with BF3 and Et3SiH at -78° in CH2C12. These reductions are completely stereoselective, and their course can be predicted by assuming a dominant stereoelectronic control of the reaction. Formation of the carbocationic intermediates 11 from 4 and 12 from 5, e.g., takes place only if the dissociating O—C bond is antiperiplanar to the donor C(β)—Fe bond. Fast H-transfer then converts the intermediate 11 to 9 and 12 to 10. The configurations of 17 and 20 can be deduced from the structure of 22 and those of 18 and 21 from that of 23. An X-ray structure determination of (1R,4S)camphanoate (-)-13 derived from alcohol (-)-7 confirms the configuration of 5 deduced above, The structures of the complexes 9 and 10, 22 and 23 were determined by their unique NMR spectra. The diastereoisomeric complexes 6 and 7 have been synthesized from aldehyde 8 with MeMgI, the diastereoisomers 17 and 18 analogously from 16 or from methyl ketone 19 by reduction with LiAlH4. Optically active starting materials (+)-1, (-)-13, (+)-20, and (+)-21 gave, by ionic hydrogenation, the complexes (-)-(3R)-3, (+)-(2S,4S)-10, (-)-(R,R, S)-22, and (-)-(R,R,R)-23 respectively, with known absolute configurations.

Notes: Using extended Hückel wave functions, molecular electrostatic potentials (MEP's) have been calculated for several model clusters representative of zeolites of offretite type. The clusters studied, which are all made of a central unit comprising 2 AlO4 and 16 SiO4 tetrahedra, differ only by the relative positions of the Al-atoms occupying the same crystallographic sites (T2) within the zeolite framework. using the MEP values as a color-coded acidity index for the various clusters, three-dimensional representations of their molecular surfaces are generated as solid models on a performing computer graphics system. Important differences in acidity are predicted for the clusters which can he classified into two types according to the distribution of Al-atoms: the first one is characterized by nearly independent acid sites localized around the main channel of zeolite (Figs. 3 and 6) whereas the second one exhibits interacting acid sites located longitudinally along the channel of the same gmelinite cage (Figs. 4 and 5). The possible relationship between the structure of the clusters and their catalytic activity towards organic species is discussed.

Notes: Starting from D-glutamic acid (5), the bicyclic compounds 4a and 4b were synthesized via 17 (Schemes 1 and 2). The reaction leading to 4g and 4h with LiCuPh2 was not successful. But treatment of the N-protected model lactams 19, 21, and 22 with Li2Cu(CN)Ph2 gave the amino ketones 24, 26, and 27, respectively (Scheme 3). The desired compound 23 was obtained from 20. Conversion of the unprotected lactams 28, 31, and 32 gave the phenyl derivative 34 in excellent yields. Ester 35 was transformed to the α -amino-γ- oxo-acid derivative 36. This conversion opens a novel access to this type of compounds.

Notes: Bare Fe(I) cations act in the gas phase as dehydrosulfurization catalysts for butyl isothiocyanate by specifically coupling the S-atom with remote H-atoms from the ω and (ω - l) position of the alkyl chain. Other losses induced by Fe(I) are due to ‘remote functionalization’, the formation of ion/dipole intermediates, and insertion/β-hydrogen shift processes.

Notes: Syntheses and Chemical Properties of Heterocyclic Tetracyanodimethanes of a Heterocyclic N,N′-Dicyanodiimine and of Fully Substituted Monocyclic TetracyanodimethanesIn the presence of different bases, 4,8-diethoxy-3H,7H-benzo[1,2-c:4,5-c′]diisoxazole-3,7-dione (3) reacts with malonodinitrile or β-oxobenzenepropanenitrile to the coloured salts 4a,b and 5, respectively, which are alkylated to the tetracyanoquinodimethane-like heterocycles 2a,b and to the bis [benzoyl(cyano)methylidene]-substituted heterocycle 6 (Scheme 1). Hydrogenation of 2a,b affords the fully substituted 7a,b, and with 2-(1,3-dithiol-2-ylidene)-1,3-dithiole, 2a gives the 1:1 charge-transfer complex 8. Heterocyclic quinone 9 is transformed to the monocyarioimino derivative 10, and 3 reacts with cyanamide and NaH to the N,N′-dicyanodiimine salt 12.

Notes: Chromium Complexes with cyclo-Asx, LigandsThe interaction of [(η5C5Me4R)(CO)2Cr]2(Cr≡Cr) (1a: R = CH3 1b: R = C2H5) with yellow arsenic (As4) affords the triarsachromatetrahedranes [(η5-C5Me4R)(CO)2Cr(η3-As3)] (2a, b) as well as the 27-VE triple-decker complexes [{(η5-C5Me4R)Cr}2-(μ,η5-As5)] (3a, b) 3 is also formed photochemically from 2. 2a and 3b have been characterized by X-ray structure analyses. The cyclo-As5 ligand forms a regular arsenic pentagon.

Notes: Metal-Complexes of Biologically Important Ligands, LII. - Binding of Monosaccharides through the Isocyano and Carbene Group to the Metal Atom: Chromium(O), Tungsten(O), Rhodium(III), Iridium(1II). Palladium(I1). Platinum(ZI), and Gold(1) Complexes of 1.3.4.6-Tetra-O-acetyl-2-deoxy-2-isocyano-α-D-glucose and -β-D-glucoseStable isocyanide complexes cis-Cl2Pd(CNR)2 (2), cis-Cl2Pt(CNR)2 (3), cis-Cl2Pt(PPh3)CNR (4), [trans-(Ph3P)2Pt(Cl)CNR]+BF-4 (5), ClAuCNR (6), (OC)5CrCNR (7), (OC)5WCNR (8), (η5-C5Me5)Rh-(CNR)Cl2 (9), (η5-C5Me5)Ir(CNR)Cl2 (10) of 1,3,4,6-tetra-O-acetyl-2-deoxy-2-isocyano-α(β)-D-glucose (CNR) as well as carbene complexes ClAuC(NHR')(NHR) (11, 12) and cis-Cl2Pt(PPh3)C-(OR')NHR (13, 14) have been prepared and characterized by their IR and NMR spectra. The structure of 10 has been determined by X-ray crystal structure analysis.

Notes: Transition-Metal-Substituted Acylphosphines and Phosphaalkenes. XII. - Transition-Metal Sulfur Ylide Complexes, XXVIIzt - Conversion of a Phosphaalkenyliron Complex (η5-C5Me5)-(CO)2FeP=(SiMe3)2 into (η3-Phosphaallyl)iron Complexes by means of Me2S-(O)=CH2: Synthesis and Molecular Structures of Two Isomeres of (η5-C5Me5)-(CO)η5-P(CH-(SiMe3)2(CHC-0)}The transition-metal-substituted phosphaalkene (η5-C5Me5)-(CO)2FeP=C(SiMe3)2 (1) reacts with the sulfur ylide Me2S-(O)=CH2 (2) to afford the yellow η3-phosphaallyliron complex 4 with a syn-configuration in the organophosphorus ligand. In toluene solution at 40°C this complex undergoes an isomerization to the corresponding anti-configurated complex 5. Constitution and configuration of both compounds were elucidated by spectroscopic methods (IR, 1H, 13C, 31P NMR, and MS) as well as single-crystal X-ray diffraction analyses.

Notes: DiphosphabicyclobutanesTwo isomeric diphosphabicyclobutanes (5,11) are obtained by treatment of the phosphaalkenes X-P = C(Ph)Tms (1a) and X - P = CTms2 (1b) (X = halogen Tms = trimethylsilyl) with 2, Mg, or Na. Both syntheses proceed by coupling of two phosphaalkene units affording, however, two different diphospha-butadiene intermediates. 4 and 10 readily undergo isomerization reactions to form the diphosphabicyclobutanes. Irradiation of the phosphaalkenes Cp* - P = C(Ph)Tms (12a) and Cp* - P = CTms2 (12b) (Cp* = C5Me5) gives rise to a different reaction pathway. Dimerization of 12a, followed by homolytic cleavage of the Cp* - phosphorus bond and intramolecular recombination produces the butterfly compound 5, whereas homolytic cleavage of the Cp* - element bond in 12 b, followed by rearrangement and intermolecular recombination, affords the diphosphabicyclobutane 11.

Notes: Complexes (dad)2RuCl2 (1) (dad = diazadiene, RN = CR'- CR'=NR) are reduced to (dad)2Ru (2) which react with L = CO or ethylene to give (dad)2RuL (3,5). Reduction of 1b ( R' = H) with magnesium-butadiene or reaction of 2b with butadiene leads to a new type of C-C coupling of butadiene to one of the diazadiene ligands (6b). Addition of CO induces a rearrangement to 7b by a hydride shift.

Notes: The photochemical conversion of 4,4,7,7-tetramethyl-4,6,7,8-tetrahydro-2H-benzopyran-2,5(3H)-dione (1) into 3,3,6,6-tetramethyl-3,5,6,7-tetrahydrobenzofuran-4(2H)-one (4) in methanol does not - as previously assumed - proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2. This conclusion results from the finding that C-2, i. e. the CH2 group, of benzofuranone 4 stems from the solvent. Similar observations were made for other benzopyrandiones 15. A reaction sequence consisting of (a) ketene elimination from 2 with formation of 2-isopropylidene-5,5-dimethyl-1,3-cyclo-hexanedione and (b) light-induced (reductive) H . and . CH2OH addition to this intermediate followed by cyclization and dehydration to 4, is proposed for the conversion 1→4.

Notes: Synthesis of Seven- and Eight-Membered Ring-Annulated Pyridines by “Inverse” Intramolecular Diels-Alder Reaction with Trifluoromethyl-Substituted 1,2,4-TriazinesIntramolecular [4 + 2] cycloaddition reactions with inverse electron demand of trifluoromethyl-substituted 1,2,4-triazines carrying 7- or 8-membered o-alkyne side-chain dienophiles (3,8,12) lead to the synthesis of bicyclic pyridines with annulated heterocyclic seven- (5, 9, 13-15) or eight-membered rings (19, 22, 23, 26).

Notes: Syntheses and Structures of New 2,2′-Bipyridine Complexes of Niobium, Molybdenum, Tungsten, and Rhenium in High Oxidation StatesExchange of oxo for chlorine ligands by means of hexamethyl-disiloxane provides an easy and effective synthesis of the oxo halides (bipy)MVOCl3 (bipy = 2,2′-bipyridine, C10H8N2; M = Nb, 1c; Re, 2c; W, 3c) and (bipy)MVIO2Cl2 (N = Mo, 6a;W, 6b). Starting from ReCl5 the structurally (X-ray) characterized byproduct (bipy)ReIVCl4 (2b) is also formed. Dirhenium heptaoxide (7) is converted into the complex (bipy)ReVIIO3Cl (8) upon treatment with chlorotrimethylsilane in the presence of 2,2′-bipyridine, thus being now easily available a key compound in rhenium chemistry. The new imido complexes of composition (bipy)MoVI(NR)2Cl2 [R = C(H3)3, 9a; C6H5, 9b] are accessible from 6a and the corresponding silylated amines. The rhenium and tungsten complexes 2b and 6b, resp., exhibit octahedral structures in the crystal, with that of 6b being distorted as a result of different ligands and intermolecular contacts.

Notes: Unusual Reaction of a Diazaphosphetidinethione with Trimethylsilyl Azide2-Dimethylamino-1,3-dimethyl-1,3-diaza-2-phosphetidine-4-thione (1) and trimethylsilyl azide do not react with formation of the expected phosphane imine 2. Instead, (a) addition of trimethylsilyl azide to the °C=S group of 1, (b) sulfurization of the phosphorus atom of 1 and formation of the racemic thiophosphoryl compound 3 (as a result of intramolecular methyl/trimethylsilyl migration) take place. For 3 two pairs of diastereomers are discussed, which have been studied by 1H-, 13C- and 31P-NMR spectroscopy, and through a 1H-13C NMR correlation.

Notes: Photoexcited 1-naphthaldehyde (1a), 1-acetonaphthone (1b), and 1-naphthophenone (1c) add α-morpholinoacrylonitrile (2a) in a [4 + 2] mode with exceptional regio- and stereoselective formation of only one diastereomer of the two possible regioisomeric 1,4-dihydro-1,4-ethanonaphthalene adducts. An independently formed 1,2-adduct 4 was detected and isolated in very low yield, 4 is thermally and photochemically (313-nm, excitation) cleaved into the starting materials with no indication of direct interconversion into 3b. Compound 3b is stable towards 313-nm radiation, but is efficiently isomerized to give the dihydrobenzosemibullvalene 7 upon 254-nm excitation. - All observations point to the first excited triplet state as the starting point for the 1,4-additions.

Notes: The molecular structures of the four Dewar benzene derivatives 4-7 were determined by means of X-ray diffraction. The central C1-C4 bonds are extremely long. The carboxylate groups on the bridgehead carbon atoms of 4, 5, and 7 are in optimal orientation for an electronic interaction with the central bonds having high p-character. Therefore the central bonds in 4, 5, und 7 (1.602-1.612 Å) are even more elongated than in 6 (1.563 Å). Repulsion between tert-butyl groups causes bond lengthening and structural deformations. The sp2-hybridized carbon atoms are pyramidalized. From structural comparison of Dewar benzene derivatives a strong correlation between the length of the central bond and the folding angle of the four-membered rings can be derived. A new rule has been established for the thermal stability of Dewar benzene derivatives.

Notes: New Watersoluble Macrobicyclic CavitiesThe watersoluble macrobicyclic compounds 1, 3, 5a, and 5b have been synthesized for the first time bearing large endolipophilic cavities of different sizes and shapes. They were studied with respect to their interactions towards lipophilic guest compounds. The “in/out” isomerism of the hitherto largest endolipophilic cavities 4a, 4b, 5a, and 5b has been investigated by 1H-, 13C-NMR spectroscopy and FAB mass spectrometry. The absence of significant 1H-NMR high-field shifts in hostguest studies is attributed to the rigidity of cavities 1 and 3, whilst the isomeric cavities 5a and 5b contain very large openings. Orientational fluorescence spectroscopy investigations, however, suggest hostguest interactions of the isomers 5a and 5b with ammonium 8-anilino-1-naphthalenesulfonate (8,1-ANS).

Notes: Electrophilic β-Bromination and Nucleophilic α-Methoxylation of α,β-Unsaturated Carbonyl CompoundsOximes 29a, b, semicarbazones 11a-d, dimethylhydrazones 4, and [3-methyl-2(3H)-benzothiazolylidene]hydrazones 23a-c of unsaturated aldehydes and ketones are brominated at the β-carbon by an addition-elimination sequence (→ 21a,b, 13a-d, 7, and 27c, respectively). When unsaturated ketone hydrazones are treated with bromine and methanol the α-methoxy-β-bromo derivatives 35a-c are obtained, which after hydrolysis and hydrobromic acid elimination give α-methoxy substitution products 36a-c of the starting compounds.

Notes: We determined the difference electron densities [X-X] in the bonds of a Dewar benzene derivative from low temperature X-ray data (94 K). The density maxima on all bonds are significant. The central bond with an internuclear distance of 1.594 Å has a strong bending character. From the difference densities a bending angle of 28° can be derived.

Notes: Stereoselectivity of Intramolecular Diels-Alder Reactions of 1,7,Q-Decatrien-3-ones to Octalone Derivatives2-Alkenyl-substituted 2-siloxycyclopropanes 1 and 2 serve as protected enone equivalents and are converted into key building blocks 5-8 in excellent yields. After desilylation and ring cleavage these compounds provide 1,7,9-decatrien-3-ones 9-12, which undergo smooth intramolecular Diels-Alder reaction at room temperature or approximately 100°C. The resulting octalone derivatives 13-16 are formed with exclusive or preferred cis connection of the rings. The relative configurations of the cycloadducts are secured by equilibration experiments and NMR spectroscopy (selective proton decouplings). For 11 → 15 and 12 → 16 the cis selectivitiy can remarkably be enhanced by trifluoroacetic acid catalysis. This high noninduced diastereoselectivity is caused by the endo approach of the reactive molecular sites, whereas the configuration of the third stereogenic centre (C-2) is determined by the folding of the linking carbon chain. Preference of a boat conformation with equatorial ester group endo-Beq may be assumed and appears to be general for intramolecular cycloadditions of such trienones. This effect as well as the influence of further substituents at the diene or dienophile portion on stereoselectivity and the reactions of other model compounds are discussed.

Notes: Non-template [2+2] condensation of terephthalaldehyde with bis(3-aminopropyl)amine and N,N'-bis(3-aminopropyl)-1,2-diaminoethane leads to macrocyclic systems that can be reduced and derivatized further, whereas a similar reaction with bis(2-aminoethyl)amine leads to polymeric material only.

Notes: Deuterated Bicyclo[3.2.0]heptan-2-ones and their NMR Spectra[3,3-2H2]-, [6,7-2H2]-, [6,6-2H2]-, and [7,7-2H2]bicyclo[3.2.0]heptan-2-ones were prepared, starting from 2-cyclopenten-1-one (1). Using these derivatives, the 13C- and 1H-NMR spectra of bicyclo[3.2.0]heptan-2-one (2) have been assigned.

Notes: Contribution to the Chemistry of Boron, 201. - Boration of Lactams and Ureas by an Amino-Imino-BoranePyrrolidon reacts with (tert-butylimino)(2,2,6,6-tetramethylpiperidino)borane (1) to give the N-borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′-triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.

Notes: Lithium Compounds of a Chlorosilanol and of Fluoro-Functional Siloxanols; Synthesis and Crystal StructuresThe lithiated disilanol (CMe3)2Si(OH)2 (1) serves as a starting material in the reaction with halosilanes for the stepwise construction of siloxanols (4, 5, 7). 4 and 7 react with n-C4H9Li to give the lithium compounds 6 and 8, respectively. 6 crystallizes in hexane as a trimer with planar three-coordinated lithium, bonded to two Si-O atoms and one Si - F atom. 8 reacts in THF with LiF elimination to give cyclotrisiloxane 9. The chlorosilanol 2 is prepared by hydroxy-chlorine exchange in 1 with PCl5. The stable lithium derivative of 2 (3) forms a dimeric THF adduct with tetrahedral lithium.

Notes: In basis media, 4-substituted pyrimido[6,1-a]isoquinolin-2-imine hydrochlorides (4) constitute an equilibrium system involving the tautomeric forms characteristic of pseudobases 5, 6, 7 and the anhydro base 9. In aqueous solution in the pH range 7-13 the ammonium hydroxide form 5 is present. Between pH 13 and 14 the pseudobase 6 probably arises from this by covalent binding of the hydroxy group. 6 is then converted to the more stable imino type anhydrobase 9. Ring cleavage of 4 by excess alkali or of 9 by a small amount of water gives 1-(acylamidinomethylen)isoquinolines 7. Compounds 7 and 9 are stable in the solid state or in aprotic solutions but revert to cation 5 in dilute protic solutions.

Notes: The title compounds 1-3 and their methyl derivatives 4-7 were synthesized 2,11-dithia[3.3]pyrazinophanes 24-26 or by Hofmann 1,6-elimination of the appropriate [(5-methyl-2-pyrazinyl)methyl]trimethylammonium hydroxides followed by dimerization of the generated 2,5-dihydro-2,5-dimethylenepyrazines. α-Chlorination of the methylpyrazines 8-10 with N-chlorosuccinimide gave the required precursors 11, 12, 14, 17 and 18. The results of the X-ray structure determinations for 1-4 and 7 which indicate an unequivocal isomer assignment are discussed with regard to steric strain in these molecules. The electronic spectra of the pyrazinophanes 7-7 are reported and compared with those of the parent methylpyrazines.

Notes: The stereochemistry of Wittig-Still rearrangements under the influence of an allylic stereogenic center attached to Bn2N or RNBoc groups is studied. Rearrangements are subject to stereocontrol through asymmetric induction. Stannylated allyl ethers 13 with Z double bonds give syn-configuration amino alcohols 15 exclusively (ds 〉95 : 〈 5 - 〉 99.8 : 〈 0.2). Stannanes of E configuration 14 lead to 15 less selectively (syn :anti = 46 : 54 - 92 : 8). X-ray structural data are provided for amino alcohol syn-15b and for the bis(carbamate) 17.

Notes: Hetero π-Systems, la. - Highly Substituted 2,4-Di-tert-butyl-l-boracyclohexadienesBoracyclohexadiees 14 and 16 with three bulky groups should be ideal starting materials for the preparation of kinetically stabilized borabenzene derivatives. They are formed by substitution reactions of anion 11, which itself is derived from 2,4-di-tert-1-methoxy-1-bora-2,5-cyclohexadiene (10) by lithiation. Reaction of lithium compound 11 with ferrous chloride provides the sandwich-type complex 12. As shown by X-ray structure analysis, 12 has C2 symmetry with the boron atoms in a syn arrangement in staggered conformation, an unusal feature for borabenzene complexes. Exchange of the methoxy group in the trimethylsilylated substance 16 leads to compounds 18a, 18b, 18c, 18d. Pyrolyses of the various precursors are described.

Notes: Synthesis of Angularly Annulated Tetraquinanes by Photo-Thermo Metathesis of Diastereomerically Pure Adducts Between Benzoquinone and TetrahydropentalenesA retrosynthesis is presented for an angularly fused tetraquinane, the central step of which is the photo-thermo metathesis of a tetrahydropentalene - benzoquinone adduct. A sequence of Michael addition/condensation reaction gives the 3-methyl- l-phenyl-1,2-dihydropentalene (2) in 70% yield from benzalacetone and cyclopentadiene. Reaction with lithium aluminum hydride lead to a 1.0: 1.0:0.8 mixture of the 1,2,3,4-tetra-hydropentalenes 4a and 4b and the 1,2,3,5tetrahydropentalene 5. This reaction is highly diastereoselective (d.s. 〉 96%) and provides the cis compounds exclusively. Diels-Alder cycloadditon of 4a, b and 5 to benzoquinone also proceeds highly stereoselectively. The adducts 7a, b and 8 may be separated by fractional crystallization. Their relative configuration can be determined by means of 2D-COSY and NOE experiments. The endo arrangement is demonstrated by the photoreactivity of the cycloadducts. Gas-phase thermolysis (700°C/0.05 Torr) of the cage molecules 9a and 9b (from irradiation in benzene) gives the angularly annulated tetraquinanes 10a and 10b in 95 and 88% yield, respectively.

Notes: Transition-Metal-Substituted Diphosphenes, XVIII1). - On the Reactivity of the Diphosphenyl Complex (η5-C5Me5)(CO)2Fe - P=P - Aryl (Aryl = 2,4,6-tBu3C6H2) with Electron-Deficient Alkenes. X-ray Analysis of the Diphosphetane The transition-metal-substituted diphosphene (η5-C5Me5)(CO)2Fe - P=P - Aryl (1) reacts with fumarodinitrile (2a) to give the 1,2 diphosphetane all-trans- as the result of a [2 + 2] cycloaddition. Similarly, compound 1 is converted by either dimethyl fumarate (2b) or dimethyl maleate (2c) into the same cycloadduct all-trans- (3b). Diphosphetane 3a was completely characterized by a single-crystal X-ray analysis.

Notes: A New Approach to Enantiomerically Pure β-Lactams from a-Amino Acids by Applying the Isonitrile-Nitrile Rearrangement(S)-Phenylalanine (1) was converted into (S)-3-benzyl-2-azetidinone (8b) by a multistep reaction sequence. The key step of this approach is a stereospecific isonitrile-nitrile rearrangement (3 → 4) by flash pyrolysis, which may be performed in 20-g batches of 3. An improved procedure for the preparation of (S)-Phenylalaninol (2a) is described.

Notes: Alkyne-Bridged Tetranuclear Clusters by Expansion of Trinuclear ClustersUnder photochemical activation Fe2(CO)9 is a suitable reagent for the expansion of alkyne-bridged trinuclear clusters 1-7 (Fe3, FeCo2, FeNi2, RuCo2, FeCoNi, RuCoNi, RuCoMo) to the corresponding tetranuclear clusters 9-15 containing Fe(CO)3 building blocks. The analogous incorporation of RhCp building blocks was possible by heating RhCp(CO)2 together with the alkyne-bridged Fe3, FeCo2, RuCo2, RuCoMo, and RuCoW clusters 1, 2a, 4, 7, and 8. The resulting clusters 16-20 with octahedral M4C2 frameworks showed framework isomerism in two cases [RuFeCo2 (11a, b) and RuCoMoRh (19a, b)]. Crystal structure determinations were performed for the Fe4 and Fe3Rh clusters 9, 16 as well as for both isomers 19a, b of the RuCoMoRh cluster.

Notes: Hydrogen Transfer Reactions, 15lI. - On the Transition State in the Dehydrogenation of Dihydroarenes by QuinonesIn the hydride abstraction from 1,2-dihydronaphthalene by o-chloroanile the regioselectivity correlates with the stability of the carbenium ions as shown by both kinetic tests and reactions of isotopomeric hydrogen donators. - The temperature dependence of primary isotope effects does not correspond with any of the categories for the transition state as proposed by Kwart2). This was examined for 1,4-cyclohexadiene and 9,10-dihydroanthracene by a Bell correction and the parameters of activation (AH/AD und [ΔEA]D/H). A VAT mechanism3) is proposed to explain both these results and the large primary isotope effects.

Notes: Heteroaromatic N-oxides and nitrones were readily and selectively deoxygenated to the corresponding bases or imines in excellent yields with the TiCl4/NaI reagent system.

Notes: Optical resolution of 22 [2,2]paracyclophane derivatives was examined by high-performance liquid chromatography (HPLC) using tris(3,5-dimethylphenylcarbamates) of cellulose and amylose as chiral stationary phases. Most compounds were completely separated into enantiomers at least on one of the stationary phases. The preparation of hte new cyclophane derivatives 10, 11, 12, 14, 16, and 19 as wel as a new procedure for the synthesis of 4-fluoro-[2,2]paracyclophane (3) are described.

Notes: Pentamacrocyclic Tris-Crown Hosts. - Selective Binding of Cationic, Anionic, and Neutral Guest CompoundsThe tris-crown host compounds 1-4 were synthesized for the first time. The X-ray crystal structures of 2 and of the 1:3 complex of 1 and KSCN were determined. Whereas in the free crown 2 a less well preorganized molecular cavity is encountered, in the complex of 1 with KSCN one potassium ion is bound to each crown ether unit. One of the three SCN- anions is situated in the interior of the cavity and in addition is disordered in such a way as to be bound to the K+ using partially the S atom of the SCN- ion. Organic guest molecules like 1,2-, 1,3-, 1,5-, 2,6-, and 2,7-naphthalenediol as well as β-naphthol in acidic water solution are bound selectively in the interior of the cavities of the host molecules 2 and 3, but not by 1 and 4, the cavities of which seem to be too small and too large, respectively. In contrast, the binding of α-naphthol and of smaller phenolic guest molecules like phenol, resorcinol, pyrocatechol, phloroglucinol, pyrogallol, and 1,2,4-trihydroxy-benzene with the host 1-4 is much less pronounced (1H- NMR highfield shifts).

Notes: Radical-Type Cyclisation of Dienes, 111. - Radical-Type Cyclisation of (R)-( - )-Carvone - On the Influence of Charge- Transfer Interactions on the Optical RotationUnder the conditions of radical cyclisation, a 1:1 diastereomeric mixture of (1R,2S,5R,R)-(+)- (2a) and (1R.2S,5R,6S)-(+)-6-methoxy-2,6-dimethylbicyclo[3.2.1]octan-3-ones (2b) is obtained from (R)-(-)-carvone in 70% yield. the configuration fo 2a and 2b were confirmed by X-ray structure analyses of their hydrazones 2d and 2e. The regio- and stereoselectivity of the radical cyclisation of 1 to 2a and 2b are discussed. The high value of the specific rotation [-555] of 2d is traced back to charge-transfer interactions between the endo-standing methoxy group at C-6 as electron donor and the dinitrophenyl-hydrazone group as electron acceptor.

Notes: Phosphorus Compounds with Unusual Coordination, 43. - Highly Functionalized λ3-Phosphinines from 5,5-Dimethoxycyclopentadienes and Kinetically Stabilized Phosphaalkyne1,2,3,4-Tetrachloro-5,5-dimethoxycyclopentadiene (5) is transformed into the λ3-phosphinine 10 by reaction with the phosphaalkyne 6; the bicyclic compound 7 is assumed to be the intermediate of the process. In an analogous way the reaction 14 + 6 yields the isomeric λ3-phosphinines 15 and 17.

Notes: The mechanisms of the deceptively similar gas-phase chemistry of amine complexes RC(CH3)2CH2NH2/M+ (R = H, CH3 M = Fe, Co, Ni) are uncovered by the use of deuterium-labeled compounds. It is demonstrated that the details of CH/CC bond-activation reactions are strongly metal-ion-dependent, as is the product distribution itself.

Notes: Antiaromatic Compounds, 26 - A Cyclobutadienecarboxylate as a Hetero-1,3-diene in Diels-Alder Reactions with 2H-AzirinesThe cyclobutadienecarboxylic ester 1 adds 2H-azirines (2a-1) to yield the oxaazatricyclic compounds 4a-f. Under thermolysis conditions cleavage of isobutylene and formation of tricyclic ketones occurs (4a, c-e → 7a-d). The Dear pyridone 11 arises from the photolysis of 7a. The structures of compounds 4b and 11 are confirmed by X-ray crystal structure analyses.