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Notes: A new protected 2-deoxy-D-ribose derivative, 5-O-[(tert-butyl)diphenylsilyl]-2-deoxy-3,4-O- isopropylidene-aldehydo-D-ribose (5), was synthesized starting from 2-deoxy-D-ribose. This compound was coupled with 2-lithio-4-(4,5-dihydro-4,4-dimethyloxazol-2-yl)pyridine giving a D/L-glycero-mixture 7 of 5-O-[(tert-butyl)diphenylsilyl]-2-deoxy-1-C-[4-(4,5 -dihydro-4,4-dimethyloxazol-2-yl)pyridin-2-yl]-3,4-O-isopropylidene- D-erythro-pentitol. The mixture 7 was 1-O-mesylated with methanesulfonyl chloride and subsequently treated with CF3COOH/H2O and ammonia to afford the α/β-D-anomers 10 of 2-(2-deoxy-D-ribofuranosyl)pyridine-4-carboxamide. Both anomers were purified and separated by HPLC and identified by NMR and DCI-MS. Anomer β-D-10 was evaluated against a series of tumor-cell lines and a variety of viral strains. No antitumor or antiviral activity was observed.

Notes: The synthesis of 4-(methylthio)-1H-imidazo[4,5-c]pyridine 2′-deoxy-β-D-ribonucleosides 2 and 9 and the conversion of the N1-isomer 2 into the 2′,3′-didehydro-2′,3′-dideoxyribonucleoside 3a or (via 7) 3-deaza-2′-deoxyadenosine (1) is described. Phosphonate building blocks of 1 were employed in solid-phase synthesis of self-complementary base-modified oligonucleotides. Their properties were studied with regard to duplex stability and hydrolysis by the restriction enzyme Eco RI.

Notes: Under the influence of an electric field, trialkyltin compounds of the type R3SnX behave as electrically neutral carriers for anions in poly(vinyl chloride) liquid membranes. The interaction of tinorganic compounds with oxoanions was studied in organic phase by means of 119Sn-NMR-monitored titrations. In the case of tributyltin chloride, no appreciable amount of complex was formed with hydrogensulfate, whereas dihydrogenphosphate gave rise to a new species. Dioctyltin dichloride and dioctyltin dioctyltin diacetate formed a 1:2 (salt/ligand) complex with hydrogenphosphate.

Notes: In general, reaction of 3-(2-substituted phenyl)sydnones with HCl gives products derived from cleavage of the sydnone ring to the corresponding hydrazine and subsequent cyclization to the side chain. In one case, 3-(2-aminophenyl)sydnone (43), the product obtained, l-amino-lH-benzimidazole (47), apparently results from nucleophilic interception by the side chain prior to complete cleavage of the sydnone ring.

Notes: Successive treatment of N-acylsultams 3 with sodium hexamethyldisilazide, 1-chloro-1-nitrosocyclohexane (1), and aq. HCl gave diastereoisomerically pure, crystalline N-hydroxyamino-acid derivatives 5. These were converted into various amino acids 7, N-hydroxyamino acids 8, and an N-Boc-amino acid 9. (S, S)-Isoleucine (17) and (S, S)-2-acetamido-3-phenylbutyric acid (23) were obtained from N-crotonoylsultam 15 via 1,4-addition of an organomagnesium or organocopper reagent followed by enolate ‘amination’ with 1.

Notes: The tricarbonylchromium complex of cyclopropa[b]naphthalene (3a) is deprotonated at C(1) with BuLi. Quenching of the resulting anion with Mel results in a 1:1 mixture of stereoisomeric methyl derivatives 6a and 6b. Peterson olefination of the bis-silylated complex 3b affords the complexed alkylidenecycloproparene 5 in low yield. The tricarbonylchromium complex of cyclopropa[b]anthracene (10) is accessible via bis-hydro-desilylation of 9. Its X-ray structure is also reported. All attempts to synthesize a tricarbonylchromium complex of benzocyclopropene (11a) failed.

Notes: High-density cell-suspension cultures of Rauwolfia serpentina cultivated in a nutrition medium optimized for the production of the glucoalkaloid raucaffricine synthesize hydroquinone glycosides from continuously added hydroquinone with a total yield of 23.87 g/1 (18 g/1 of arbutin and 5.87 g/1 of a hydroquinone diglycoside) in 7 days. This arbutin production is by far the highest formation of a natural product by plant-cell-culture systems reported to date.

Notes: It is shown that azulenes react with dimethyl acetylenedicarboxylate (ADM) in solvents such as toluene, dioxan, or MeCN in the presence of 2 mol-% [RuH2(PPh3)4] already at temperatures as low as 100° and lead to the formation of the corresponding heptalene-1,2-dicarboxylates in excellent yields (Tables 1 and 2). The Ru-catalyzed reaction of ADM with 1-(tert-butyl)-4,6,8-trimethylazulene (31) takes place even at room temperature, yielding the primary tricyclic addition product 32 and its thermal retro-Diels-Alder product dimethyl 4,6,8-trimethylazulene-1,2-dicarboxylate (21; Scheme 4). At 100° in MeCN, 32 yields 90% of 21 and only 10% of the corresponding heptalene. These observations demonstrate that [RuH2(PPh3)4] catalyzes the first step of the thermal formation of heptalenes from azulenes and ADM which occurs in apolar solvents such as tetralin or decalin at temperatures 〉 180° (cf. Scheme 1).

Notes: A new, convenient, and safe route to 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) was investigated by hydrogenation of azo-coupled derivatives of phloroglucinol. In the presence of acetic anhydride, the reduction of trisphenylazophloroglucinol (H2/Pd(5%) on C) resulted in the formation of tri-, hexa-, and nona-acetylated derivatives of triaminophloroglucinol. All three compounds are air-stable, colorless solids. However, the succeeding hydrogenation to the cyclohexane derivative failed. Trisodiumtris(p-sulfonatophenylazo)phloroglucinol could be hydrogenated in a one-pot reaction to the desired taci· 1.5H2SO4 using a Pt/Rh oxide as catalyst. taci provides two distinct chair conformations with either three amino or three hydroxy groups for metal binding. The unique metal-binding properties are discussed in terms of minimal conformational changes required for coordination. Conformational analysis, based on X-ray structural data of [BiCl6][H3(taci)] ·2 H2O (Pnma, a = 24.314 (5) Å, b = 10.215 (2) Å, c = 7.422 (8) Å, R = 5.8%) and [Co(taci)2(NO3)3]·2H2O (C2/c, a = 22.912 (8) Å, b = 8.942 (2) Å, c = 14.731 (3) Å, β = 128.66 (2)°, R = 4.9%) and the previously investigated [Cr(taci)2]3+ revealed an almost ideal chair conformation in all three molecules.

Notes: Reaction of 3-bromo-3-methylbutan-2-one (1) with mercapto-esters 2 affords 5-oxo-3-thiahexanoates 3 which cyclize to thiane-3,5-diones 4. Conversion of these dicarbonyl compounds to their ethyl enol ethers 5-7 followed by reduction with LiAlH4 gives 2H,6H-thiin-3-ones 8-10. On irradiation (350 nm) in either MeCN, benzene, or i-PrOH, these newly synthesized heterocycles isomerize efficiently to 2-(alk-l-enyl)thietan-3-ones 11-13. The rearrangement seems to proceed from an excited singlet state, as it is not quenched by naphthalene, and also occurs with the same efficiency in the presence of added alkene. A (9-S-3) sulfuranyl-alkyl biradical formed by bonding of C(α) of the enone C=C bond on sulfur is discussed as possible intermediate.

Notes: Derivatives of 2-chloro-2′-deoxyadenosine (1a) containing secondary 6-NH2 groups (5a-c) or a 8-Br substituent (9) were synthesized. They were tested together with ring-modified congeners containing a pyrrolo[2,3-b]pyridine, pyrrolo[3,2-c]pyridine, or pyrazolo[3,4-d]pyrimidine ring system as inhibitors of various leukemic cell lines. Only the 8-Br derivatives 9 showed inhibitory activity, whereas the base-modified congeners were not active. Compound 1a was protonated at a pKa = 1.4 (2′-deoxyadenosine at pKa = 3.8). Protonation occurred at N(7) and not at N(1) as observed for dA.

Notes: Five- and Six-Membered Cyclic Phosphonic Diamides, Thioester-amides and Spirobi[oxazaphospholes]By reaction of the 1,2-diaminobenzene derivatives 1a-d with the phosphonoyl dichlorides 2a-g, the 1,3-dihydro-1,3,2-benzodiazaphosphol-2-ones 4a-q are obtained. The phosponoyl dichlorides 2a-e, 2g, and 2h yield with naphthalene-1,8-diamines (5) the diazaphosphinones 6a-g under similar reaction conditions. The thiazaphosphole oxides 9a-d are accessible by reaction of the phosphonoyl dichlorides 2a-d with 2-aminobenzenethiol (7). Unexpectedly, the reaction of the dichlorides 2a and 2b with 2-aminophenol (10) led to the spirobi[oxazaphospholes] 13a and 13b, respectively.

Notes: The cyclopalladation of two different types of aniline derivatives is described: the acetylated anilines N-(3-methylphenyl)acetamide (2a), 3-(acetylamino)-4-chlorobenzoic acid (2c), and N-(2-chlorophenyl)acetamide (2d) are cyclometalated easily with palladium(II) acetate and trifluoroacetic acid to yield the corresponding complexes 4a, 4c, and 4d, respectively, whereas the acetylated meta-toluidine N-(2-chloro-5-methylphenyl)acetamide (2b) cannot be metalated at the only accessible site between the acetylamino and the methyl group. This aromatic C—H bond can be activated, however, with the second type of meta-toluidine derivatives: the 2-chloro-5, N-dimethyl-N-nitrosoaniline (3b) readily undergoes cyclopalladation to yield the corresponding PdII complex di-μ-trifluoro-acetato-bis[3-chloro-6-methyl-2-(N-methyl-N- nitrosoamino)phenyl-C,N—O]dipalladium(II) (5b) containing a five-membered palladacycle with coordination of PdII at the nitroso N-atom, which is established by 15N-NMR spectroscopy.

Notes: Optically active 1,3-O-disubstituted glycerols were obtained by enantioselective homogeneous hydrogenation of the corresponding 1,3-O-disubstituted 1,3-dihydroxypropan-2-ones with different RuII-binap complexes. The highest enantioselectivities were obtained with dimeric chloro-ruthenium complexes on the substrates bearing bulky trityloxy groups.

Notes: The synthesis and 1H-NMR and electronic absorption spectra of 4,8,9b-triazacyclopenta[c, d]phenalene and several of its derivatives are described.

Notes: The sandwich complexes bis(η6-naphthalene)molybdenum(0) (1), bis(η6-1-methylnaphthalene)molybdenum(0) (2), and bis(η6-1,4-dimethylnaphthalene)molybdenum(0) (3) are synthesized by cocondensation of Mo-atoms with the naphthalene ligands. Complexes 1-3 are also obtained by reduction of MoCl5 or MoCl4. 2THF with highly activated Mg in the presence of the naphthalene ligands. Mg was activated by sublimation of the metal in a simple rotating solution reactor. Complex 2 exists as a mixture of regio- and stereoisomers. Three regioisomers, 3a-c, are formed in reactions of Mo-atoms with 1,4-dimethylnaphthalene, whereas 3a, the isomer with the Mo-atom coordinated to the unsubstituted rings, is formed selectively via the reductive method. The ligands in 1-3 are highly labile. CO displaces both naphthalene rings in 2 and 3 to give [Mo(CO)6], while PF3, P(OMe)3, and PMe3 displace only one coordinated naphthalene in 1 to yield the [Mo(η6-naphthalene)L3] complexes 4-6. In toluene, arene exchange is a competitive process in reactions of 1 with PF3. Complexes 5 (L = P(OMe)3) and 6 (L = PMe3) react with HBF4 to give the cationic metal hydride complexes 8 and 9. The X-ray crystal structures of [Mo(η6-naphthalene) {P(OMe)3}3] (5) and [Mo(H)(η6-naphthalene) {P(OMe)3}3][BF4] (8) are reported.

Notes: Vicinal deuterium-induced 6Li-NMR isotope shifts have been found for (D5)phenyllithium. These shifts are to low field, and their magnitude varies from 7 to 19 ppb with different solvents and donor molecules. On the basis of the isotopic fingerprints observed in the 6Li-NMR spectra of C6H56Li/C6D56Li mixtures, the aggregation behaviour of phenyllithium under different solvent conditions and in the presence of amines as donor ligands (TMEDA, PMDTA) was studied. Tetramers and dimers are observed in Et2O, dimers as well as momomers in Et2O/TMEDA and in THF, and momomers in THF/PMDTA. The hitherto unidentified species in Et2O/TMEDA was shown to be a monomer.

Notes: The question of how far one can go in the determination of conformation with the sole use of coupling constants as restraints in MD simulations was addressed. Couplings are being used ever more frequently as constraints as measuring heteronuclear long-range coupling constants becomes easier. For this investigation, cyclosporin A, which has previously been extensively examined with NOE-restrained simulations, is used as a model system. Many additional one-and three-bond coupling constants have been measured. The MD simulations were carried out with the addition of a potential-energy penalty function based directly on the Karplus curve. It is shown that, for dihedral angles with more than one coupling, the restraints are very efficient, in agreement with the structure observed from NOEs. However, it turned out that the structure of CsA is not adequately described, when only J couplings are used.

Notes: ortho-Substituted [Cr(CO)3(benzaldehyde)] complexes are obtained via nucleophilic addition of alkyl- and aryllithium reagents to a [Cr(CO)3(phenylmethaneimine)] complex followed by endo-hydride abstraction with triphenylmethyl cation. This sequence, when carried out with a [Cr(CO)3(benzaldehyde SAMP hydrazone)] complex affords substituted derivatives (Me, Bu, Ph, vinyl) with high (≥97%) diastereoselectivity and, after hydrolysis, ortho- substituted [Cr(CO)3(benzaldehyde)] ((S)-1) complexes of high enantiomeric purity.

Notes: Synthesis and Behaviour of Isoflavones Substituted in 2′-PositionThe protected chalcones 6-8 prepared from acetophenone and benzaldehydes rearranged to the dimethoxypropanone derivatives 9-11 in the presence of trimethyl orthoformate by Tl(NO3)3. 3 H2O. These compounds could be cyclized to the isoflavones 12-14 in high yields (Scheme 2). The conversion of these isoflavones to the corresponding isoflavanes (model compounds of the phytoalexin glabridin; see Scheme 1) was the main goal of this work. Hydrogenation of 13 and 14 gave the isoflavanes 15 and 16, respectively and their deprotection the racemic natural product 4′-O-demethylvestitol (17). Reduction of 13 and 14 yielded different compounds depending on the reducing agent (Scheme 3). The saturated alcohols 20-23 could be obtained with NaBH4 or LiBH4. They were transferred into the racemic 9-O-demethylmedicarpin (24) and haginin D (25) under acidic conditions. The ketones 26-28 (Scheme 4) were obtained in high yields by reduction of 12-14 with DIBAH. Deprotection of 26 yielded the racemic 2,3-dihydrodaidzein (29). Compounds 13 and 27 as well as 20 and 22 showed different behaviour under reduction conditions with Li in liquid ammonia. An efficient method for the introduction of the MeOCH2O and the MeOCH2CH2OCH2 protecting groups into hydroxylated benzaldehydes and acetophenones (Scheme 5) is described. The appropriate experimental conditions depend on the regioselectivity and on the number of the protected groups. The protected aldehydes, especially those with a protected ortho OH group, show an extraordinary ionization behaviour in chemical-ionization mass spectrometry (isobutane; Scheme 6).

Notes: Intramolecular cyclisation of properly protected and activated derivatives of 2′,3′-secouridine ( = 1-{2-hydroxy-1-[2-hydroxy-1-(hydroxymethyl)ethoxy]-ethyl}uracil; 1) provided access to the 2,2′-, 2,3′-, 2,5′-, 2′,5′-, 3′,5′-, and 2′,3′-anhydro-2′,3′-secouridines 5, 16, 17, 26, 28, and 31, respectively (Schemes 1-3). Reaction of 2′,5′-anhydro-3′-O-(methylsulfonyl)- (25) and 2′,3′-anhydro-5′-O-(methylsulfonyl)-2′,3′-secouridine (32) with CH2CI2 in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene generated the N(3)-methylene-bridged bis-uridine structure 37 and 36, respectively (Scheme 3). Novel chiral 18-crown-6 ethers 40 and 44, containing a hydroxymethyl and a uracil-1-yl or adenin-9-yl as the pendant groups in a 1,3-cis relationship, were synthesized from 5′-O-(triphenylmethyl)-2′,3′-secouridine (2) and 5′-O,N6-bis(triphenylmethyl)-2′,3′-secoadenosine (41) on reaction with 3,6,9-trioxaundecane-1,11-diyl bis(4-toluenesulfonate) and detritylation of the thus obtained (triphenylmethoxy) methylcompound 39 and 43, respectively (Scheme 4).

Notes: The l-azabicyclo[2.2.1]heptan-3-exo-ol (2) was resolved by fractional crystallisation of its hydrogen tartrate salts. The enantiomers (+)- and (-)-2 were oxidised to the ketones (-)-4 and (+)-4, respectively (Scheme). CD spectroscopy suggested that (-)-4 possesses the (1R,4S)-configuration. This absolute configuration was confirmed by single-crystal X-ray diffraction of the derivative (+)-(1R,4R)-3-(1,3-dithian-2-ylidene)-1-azabicyclo [2.2.1]-heptane ((+)-5).

Notes: Unusual and novel C11H16 olefins with (E)- or (E,E)-configuration instead of the previously known (Z)- or (E,Z)-configuration at the double bond(s) within the longer side chain are the main products of the Australian phaeophyte Dictyopteris acrostichoides. This configuration anomaly refers to all four series of alicyclic C11H16 hydrocarbons, namely the disubstituted cyclopentenes and cyclopropanes, as well as the monosubstituted cycloheptadienes and cyclopentenes. Chiral compounds within the above series have the same absolute configuration. The two (cyclopent-3-enyl)hexa-1, 3-dienes 11 and 13 are found for the first time. The absolute configuration and optical purity of the hydrocarbons are determined by gas chromatography on modified cyclodextrins as chiral stationary phases. The synthesis of chiral references via lipase-catalyzed resolutions is described.

Notes: Fluoro Analoga of Cycloheptadiene Pheromones of Marine Brown Algae: Exceptionally Facile [3,3]-Sigmatropic Rearrangement of a trans-Di(alkenyl)-Substituted Geminal DifluorocyclopropaneThe 3,3,-difluorocyclopropane-1,2-dicarbonyl compounds 9a and 9b are obtained by addition of difluorocarbene to methyl cinnamate or trans-stilbene followed by oxidative degradation of the phenyl rings(s) (Scheme 2). Compound 9b is a versatile building block for the synthesis of the di(alkenyl)-substituted geminal difluorocyclopropane 5 or the chrysanthemum ester 10b. Cyclopropane 5 is unstable at room temperature and rearranges to the 3,3,-difluorocyclohepta-1,4-diene 4, an analog of the algal pheromone dictyotene (1; Scheme 3). The kinetic parameters of the [3,3]-sigmatropic rearrangement are determined. The data support the view that a geminal difluoro group within a cyclopropane weakens the distal bond.

Notes: Acid-mediated cyclisation of trienone 8, readily available from 2,3-dimethylbutanal (1; five steps: 47% yield), using fluorosulfonic acid (6.8 mol-equiv.) in 2-nitropropane at -70°, afforded a 14:9:1 mixture (70% yield) of (±)-cis-α-irone (9), (±)-trans-α-irone (10), and (±)-β-irone (11). Other acidic conditions examined, using 95% aq. H2SO4 solution, 85% aq. H3PO4 solution, or SnCl4, gave inferior results.

Notes: The enantiomers of the title compound, 7a and ent-7a, and of substituted analogues are synthesized. The absolute configuration of 7a is deduced from that of (tert-butyl 2-tert-butyl)-3-methyl-4-oxoimidazolidin-1-carboxylate (15) and from the trans-configuration of the intermediate 17a which in turn is assigned on the basis of 1H-NMR nuclear Overhauser effect (NOE) measurements. Instead of 15, the 2-isopropyl-substituted analogue 21 can also be employed. Its preparation from glycine, methylamine, isobutyraldehyde, and (Boc)2O, and the resolution through the bis-O,O′-(4-toluyl)tartrate salt 20 are described. In two functional tests (rat neocortical slice and frog hemisected spinal cord preparation) the (S)-enantiomer 7a (SDZ EAB 515) is shown to be a very potent, selective competitive NMDA antagonist.

Notes: Stereoselective Synthesis of (2S,6S)-2,6-Diaminoheptanedioic Acid and of Unsymmetrical Derivatives of meso-2,6-Diaminoheptanedioic AcidSpecific inhibition of enzymes of the diaminopimelate pathway (L-lysine biosynthesis) should, in principle, lead to selective antibacterial agents or herbicides. For this purpose, enantioselective syntheses were devised for (2S, 6S)-2, 6-diaminoheptanedioic acid (L, L-diaminopimelate, 1), (2R,6S)-2,6-diamino-2-methylhept-3-enedioic acid (10), (2R, 6S)-2, 6-diaminohept-3-enedioic acid (9), (2R, 6S)-2, 6-diamino-4-fluorohept-3-enedioic acid (42), and (2S, 6S)-2, 6-diamino-3-chloroheptanedioic acid (5). The Schöllkopf bislactim-ether methodology was applied to control the configuration of C(2) and C(6) of 1, C(2) of 10, as well as C(6) of 9 and 42. Semialdehyde derivatives of L-glutamate afforded C(6) of 10 and 5, while the (R)-configurated C(2) of 9 and 42 were derived from L-serine. For this purpose, the synthesis of the Garner aldehyde 32 has been improved. As chromatographic purifications and the low temperatures for the reduction of the carboxylic acid are eliminated, this valuable intermediate can now be prepared in bulk quantities. An enantio- and diastereoselective aldol addition of a glycine titanium-enolate was applied for the construction of 5 (C(2) and C(3)). As all chiral building blocks and reagents used are available in both enantiomeric forms, these routes should also be suitable for the selective synthesis of the other stereoisomers of these bis(α-amino acids).

Notes: The X-ray structures of fifteen 1, 3-imidazolidine, 1, 3-oxazolidine, 1, 3-dioxan-4-one, and hydropyrimidine-4(1H)-one derivatives are described (Table 2) and compared with known structures of similar compounds (Figs. 1-20). The differences between structures containing exocyclic N-acyl groups and those lacking this structural element arise from the A1,3 effect of the amide moieties. Even t-Bu groups are forced into axial positions of six-ring half-chair or into flag-pole positions of six-ring twist-boat conformers by this effect (Figs. 16-20). In the N-acylated five-membered heterocycles, a combination of ring strain and A1, 3 strain leads to strong pyramidalizations of the amide N-atoms (Table 1) such that the acyl groups wind up on one side and the other substituents on the opposite side of the rings (Figs. 4-9 and Scheme 3). Thus, the acyl (protecting!) groups strongly contribute to the steric bias between the two faces of the rings. Observed, at first glance surprizing stereoselectivities of reactions of these heterocycles (Schemes 1 and 2) are interpreted (Scheme 3) as an indirect consequence of the amide A1, 3 strain effect. The conclusions drawn are considered relvant for a better understanding of the ever increasing role which amide groups play in stereoselective syntheses.

Notes: We studied the stability of the Schiff bases formed between pyridoxal 5′-phosphate (PLP) and leucine in the presence of (hexadecyl)trimethylammonium bromide (CTAB) over a wide pH range by determining the kinetic constants of formation and hydrolysis of these compounds. The results show that the stability of the Schiff bases is increased by the presence of CTAB as a result of increased rates of formation and decreased hydrolysis rate constants. The ionic head groups of CTAB favour the formation of the bases, while its hydrophobic rests protect the imine double bond from hydrolysis. This model system permits one to obtain partially hydrophobic media with no need for any non-aqueous solvents.

Notes: Photolysis of (o-allylbenzyl)dicarbonyl(η5-cyclopentadienyl)iron (4) at 20° in CH2Cl2 leads to carbon-monoxide loss followed by intramolecular complexation to [η2-(o-allylbenzyl)]carbonyl(η5-cyclopentadienyl)iron (13). At 50° in C6D6, a photochemical rearrangement proceeds forming carbonyl (η5-cyclopentadienyl){η3-[3-(2-methylphenyl)allyl]}iron (17). Depending on the temperature, photolysis of 4 leads to intermolecular reactions at the benzylic or allylic position of the π complexes 13 and 17, respectively.

Notes: Ab initio Studies on N-Acyliminium IonsThe geometric and electronic structure and reactivity of the N-formylmethyleneiminium ion are calculated in different conformations by ab initio methods and compared to those of N-methylformamide and the methyleneiminium ion. The known preferred attack of the C(5) of 3-acyl-2,3-dihydro-1,3-oxazoles by electrophiles is explained by the lower (calculated) energy of the corresponding acyliminium ion relative to that of the oxenium ion. The stereoselectivity of additions to these acyliminium ions can not be explained by our calculations. Ab initio calculations of the subsystems acyliminium and oxenium ion show that the reactivity can be predicted from investigation of these much simpler systems and make us suppose that a nitro instead of an acyl group will reverse the regioselectivity of the addition to 2,3-dihydro-1,3-oxazoles.

Notes: Oxygentation of aqueous solutions of CoIII in presence of stoichiometric amounts of N-(2-aminoethyl)ethane-1,2-diamine (dien) and 1,3-diaminopropan-2-ol (dapo) produces μ-peroxocobalt(III) dimers. Acid cleavage (HCI) yields mer-exo(H)-, mer-endo (H)-, unsym-fac-exo(OH)-, and unsym-fac-endo(OH)-[CoCl(dien)(dapo)]2+ (A-D)(X = Cl), resp. and unsym-fac-[Co-(dien)(dapo-N,N′,O)]3+ (G). Isomer seperation was achieved by fractional crystallization as ZnCl42- and ClO4- salts and by ion-exchange chromatography. The corresponding bromo, azido, nitrito-O, nitro-N, thiocyanato, hydroxo, and aqua complexes were also synthesized. Optically resolved samples were prepared for chiral compounds, and the complexes were structurally characterized by X-ray analyses (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(-)436(CD)-A (X = N3)), (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document}(-)436(CD)-B). (X = N3), \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document} (+)436(CD)-B by their chiroptical properties, and by 13C-NMR spectroscopy supported by 1H-NMR, IR, CD, and UV/VIS spectroscopy. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(-)436(CD)-mer-exo(H)-[Co(N3)(dien)(dapo)](hydrogen di-O-benzoyl-L-tartrate)2.4 H2O crystallizes in the orthorhombic space group P212121, a = 7.676(1) Å, b = 19.457(1) Å, c = 34.702(2) Å. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(-)436(CD)-mer-endo(H)-[Co(N3)(dien)(dapo)] (hydrogen di-O-benzoyl-L-tartrate)2.2.75 H2O crystallizes in the triclinic space group P1, a = 8.062(3) Å b = 10.296(1) Å, c = 15.056(2) Å, alpha = 80.55(1)°, β = 85.18(2)°, γ = 89.10(2)°. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document}(+)436(CD)-mer-endo(H)-[Co(N3)(dien)(dapo)](hydrogen di-O-benzoyl-L-tartrate)2. 5.75 H2O crystallizes in the triclinic space group P1, a = 7.742(1) Å, b = 10.014(1) Å, c = 18.045(2) Å, α = 99.57(1)°, β = 92.87(1)°, γ = 102.56(1)°. The absolute configurations of the three cations were determined unambiguously. Interconversions of the various isomers and derivatives and structural, configurational, and spectroscopic aspects are discussed in detail.

Notes: Azide anation and racemization of optically pure mer-exo(H)- and mer-endo(H)-[Co(OH)(dien)(dapo)]2+ (A and B (X = OH), resp.; dien = N-(2-aminoethyl)ethane-1,2-diamine; dapo = 1,3-diaminopropan-2-ol) involve the same symmetrical pentacoordinate intermediate as the base hydrolyses of the corresponding mer-exo(H)- and mer-endo(H)-[CoX(dien)(dapo)]2+ species A and B, respectively, where X = Cl, Br, or N3. The kinetic parameters of the anation process are fully compatible with the independently measured competition ratio. The rate data reveal that substitution of OH- is unexpectedly fast, viz. it is not consistent with the usual sequence Br- 〉 Cl- 〉 H2O 〉 N3- 〉 OH-. This behavior is interpreted on the basis of an internal conjugate base mechanism which involves an amino-hydroxo/aminato-aqua tautomerism, viz. the reaction is actually an OH- -catalyzed substitution of [CoH2O(dien)(dapo)]3+ where deprotonation occurs effectively at the secondary-amine site NH of dien.

Notes: (6,6′-Dimethyl-1,1′-biphenyl-2,2′-diyl)bis(diphenylphosphine) ( = biphemp) reacts with allymetal halidesm to yeild complexes 1-3 which were transformed into the corresponding perchlorates 4-6. The molecular structures of 4-6 were determined by X-ray analyses.

Notes: A fast electrochemical technique for the discrimination of one- and two-electron mechanisms in the oxidative addition of alkylating agents (RX) to corrinato- and porphyrinatocobalt(I) ([CoIL]) is described. It is based on single-scan voltammograms of [CoIIL] in the presence of RX and variable amounts of the radical trap acrylonitrile. In the first part of the voltammogram, [CoIIL] is reduced, and fast oxidative addition of RX to [CoIL] is triggered. If the reaction proceeds via a two-electron mechanism, [R—CoIIIL] is formed independently of acrylonitrile concentration, but if a transient free radical R is involved, R is competitively trapped by acrylonitrile and [CoIIL] to yield, at high enough acrylonitrile concentration, exclusively the olefin-inserted [RCN—CoIIIL]. [RCN—CoIIIL] is reducible in the intermediate potential range, [R—CoIIIL] at the negative end of the single-scan voltammogram. Hence, from the appearance of the reduction waves due to [RCN—CoIIIL] and [R—CoIIIL], the mechanism of oxidative addition of RX to [CoIL] is easily deduced. The method is applied to the study of the mechanistic borderline of oxidative addition using a series of 15 RX and 4 [CoL]'s, i.e. cobalamin (Cbl), heptamethyl cobyrinate (‘Cby’), (tetraphenylporphyrinato) cobalt ([Co(tpp])), and (octaethylporphyrinato) cobalt ([Co(oep)]). All non-activated primary alkyl iodides and bromides exhibit, at room temperature, pure two-electron mechanisms with all [CoIL]'s, except neopentyliodide with Cb1I and ‘Cby’I. All secondary alkyl iodides involve free radicals with Cb1I and ‘Cby’I, but a pure two-electron mechanism or a mixed one-electron two-electron mechanism with [CoI(tpp)] and [CoI(oep)]. The mechanistic switch from a two-electron to a one-electron mechanism for increasingly sterically demanding RX's occurs earlier with the supernucleophilic Cb1I and ‘Cby’I than with [CoI(tapp)] and [CoI(oep)].

Notes: Temperature-dependent NMR spectra indicate that the α-chamigren-3-ones (-)-11, (+)-12, (+)-14 (-)-15, (+)-16, 18, and 19 bearing equatorial halogen atoms at C(8) and C(9) undergo slow conformational flipping of the envelope-shaped enone ring, while the cyclohexane ring is maintained in the chair conformation. The α-chamigren-3-ols (+)-20 and (+)-21, obtained by hydride reduction of (+)-12, behave similarly, with slow half-chair inversion of the cyclohexenol ring. In each case, both conformers are about equally populated and detectable by NMR, except in the case of (+)-15, where repulsive interactions between Br—C(2) and Heq-C(7) make the population of the conformer 15b with Me - C(5) faced to Hax-C(10) so low that it escapes direct 1H-NMR detection. The energy barriers to these conformational motions are viewed to arise mainly from repulsive interactions between Me - C(5) and the axial H-atoms at C(8) and C(10), while, contrary to previous beliefs, no twist-boat conformations of the cyclohexane ring intervene. Similar conclusions hold for the 4,5-epoxides of both (-)-6 and (+)-7. Clean Jones oxidatio of (-)-2 to 17, where the CH2=C(5) bond is maintained, and acid dehydration-isomerization of the α-chamigrene (+)-21 to the β-chamigrene (+)-24, reflect the special stability of β-chamigrenes, providing a reason for their frequent occurrence in nature.

Notes: The title compound FeF+ has been generated in a Fourier-transform ion-cyclotron-resonance mass spectrometer via C—F bond activation by reacting hexafluorobenzene with bare FeO+. Bracketing experiments provide a bond-dissociation energy (BDE) for FeF+ of 86 〈 BDE 〈 101 kcal/mol. High-level CAS-MCSCF pseudopotential ab initio calculation, including 501036 electronic configurations, predict a BDF(Fe+—F) of 100.9 kcal/mol.

Notes: Base hydrolysis of optically pure mer-exo(H)- and mer-endo(H)-[CoCl(dien)(dapo)]2+ (A and B (X = Cl)), resp.; dien = N-(2-aminoethyl)ethane-1,2-damine; dapo = 1,3-diaminopopan-2-ol, kOH = (1.13 ±0.09)·105 M-1s-1 (A (X = Cl), kOH = (1.18 ± 0.11)·105M-1s-1 (B (X = Cl)); I = 1.0M (NaClO4 or NaN3)1, T = 298 K) is accompanied by retention of the mer-geometry and full racemization (99 ± 1%). It is shown this is not due to racemization of either reactants or products. This result, together with the fact that both A and B yield the same mer-exo(H)-product distribution, indicates the intermediacy of a pentacoordinate species II which is symmetrical (at least in the time average), viz. trigonal bipyramidal with a deprotonated (‘flat’) secondaryamine moiety. The H-exchange rates of the coordinated amine groups are consistent with this interpretation and indicate that loss of Cl- is the rate-determining step, in agreement with an SN1CB mechanism. The reactivity of the unsym-fac-exo(OH)- and unsy,-fac-endo(OH)-isomers C and D, respectively, is in sharp contrast: base hydrolysis is 3 orders of magnitue slower, and the reaction is accompanied by some change of coordination geometry (C, 23%; D, 10%, some inversion of configuration (C, 15%; D, 19%)); much lower acceleration of hydrolysis in base (106 vs. 1010). Azide competition during base hydrolysis of the mer-isomer A and B is quite large (R = [CoN3]∞/[CoOH]∞[N-3] = 1.4 ±0.2M-1, I= 1.0M, T = 298 K) and indicates that the coordinatively unsaturated intermediate II is highly selective. The ratios of exo(H)- and endo(H)-azide competition products A and B (X = N3), respectively, immediately after the substitution reaction (kinetic control) are independent of the engaged epierm A or B: 31.7 ± 0.9% of B (X = N3) and 68.3 ± 0.9% of A (X = N3, determined after ca. 10.t½ of the base hydrolysis). This is agreement with the effective site of deprotonation at the secondayr(central)-amine group of dien, cis to the leaving group X, and with a common set of intermediates. Epimerization of A and B (X = Cl, N3) is shown to proceed solely via the pentacoordinate (base hydrolysis) intermediate II, viz. the direct route involving a six-coordinate deprotonated intermediate is immeasurably slow. For the hydroxo products A and B (X = OH), the direct rotue may compete with the H2O-substitution(exchange) path which can occur by an internal conjugate-base process. The kinetically controlled distribution of complexes A/B (X = N3) is different from the quasi-thermodynamic one (19.1 ± 0.8% of B (X = N3) and 80.9 ± 0.8% of A (X = N3)). This is consistent with the differences in the base-hydrolysis rates of the reactants (kOh (A (X = N3))= (1.59 ± 0.04)·102M-1s-1; kOH (B (X = N3)) = (2.89 ± 0.22).102M-1s-1). Various aspects of the investigated reactions are discussed on the basis of the widely studied reaction of base hydrolysis of pentaaminecobalt(III) complexes. Also, the structure and reactivity of the pentacoordinate intermediate II are discussed in relation to various current models.

Notes: The socium cryptates of the macrobicyclic ligands 1-6 have been synthesized by direct macrobicyclisation or by stepwise procedures. They incorporate 2,2′-bithiazole, 2,2′-biimidazole, 2.2′-bipyrimidine as well as 2,2′-bipyridine units. Treatment of the sodium complexes with europium(III) chloride gave the corresponding EuIII cryptates. The structural and spectral properties of these compounds are described. The EuIII complexes present characteristic 1H-NMR chemical-shift features. Their luminescence properties are described.

Notes: The anomeric configuration of the glycosidic bond in lumazine N1-(2′-deoxy-D-ribonucleosides) 1-6 was investigated by NOE difference spectroscopy. The former configurational assignment of the α - and β -D-anomers 1 and 2, 3 and 4, and 5 and 6, respectively, has to be reversed to be in agreement with the physical data. Additional proof is presented by X-ray analysis of 3 and 6. Chemical interconversions of 1-(2′-deoxy-β-D-ribofuranosyl)-6,7-diphenyllumazine (6) into 2,3′ -anhydrolumazine 2′-deoxyribonucleosides 16 and 17 are also in agreement with the revised anomeric configuration.

Notes: The stereoselective formation of the 1:2 complexes [M(his)2] and [M(PhEt-sal)2] (M = Ni2+, Cu2+, PhEt-sal = N-(1-phenylethyl)salicylaldimine) has been determined by circular dichroism (CD) measurements. Stereoselectivity, defined as S = Kmeso/2Krac' has been found to be 2.48 for [Ni(his)2], corresponding to a 21% excess of the mixed species relative to the statistical amount. This value is temperature-independent between 15 and 35°. Whereas the absence of stereoselectivity in the formation of [Cu(prol)2] is confirmed, weak stereoselectivity is observed for [Cu(his)2] (2% excess of the mixed species). The CD intensity of the latter complex strongly depends on temperature and decreases by 12%, when the temperature is increased from 15 to 35°. Small but significant stereoselectivity is found for the formation of the Schiff-base complexes [Ni(PhEt-sal)2] and [Cu(PhEt-sal)2] in acetone with 1.0% and 2.4% excess, respectively, of the mixed species over the statistical value.

Notes: At room temperature or under reflux in MeCN, 3-amino-2H-azirines 2 and 3,4-dihydro-2H-1,2-benzothiazin-3-one 1,1-dioxide (4) give 1,2,5-benzothiadiazonin-6-one 1,1-dioxides5 in fair-to-good yield (Scheme 2). The structure of this novel type of heterocyclic compounds has been established by X-ray crystallography of 5a (Fig.). A ring expansion via a zwitterionic intermediate of type A' is proposed as the reaction mechanism of the formation of 5.

Notes: The thermal reaction of 7-isopropyl-1,3,4-trimethylazulene (3-methylguaiazulene; 2) with excess dimethyl acetylenedicarboxylate (ADM) in decalin at 200° leads to the formation of the corresponding heptalene- (5a/5b and 6a/6b; cf. Scheme 3) and azulene-1,2-dicarboxylates (7 and 8, respectively). Together with small amounts of a corresponding tetracyclic compound (‘anti’-13) these compounds are obtained via rearrangement (→ 5a/5b and 6a/6b), retro-Diels-Alder reaction (→ 7 and 8), and Diels-Alder reaction with ADM (→ ‘anti’-13) from the two primary tricyclic intermediates (14 and 15; cf. Scheme 5) which are formed by site-selective addition of ADM to the five-membered ring of 2. In a competing Diels-Alder reaction, ADM is also added to the seven-membered ring of 2, leading to the formation of the tricyclic compounds 9 and 10 and of the Diels-Alder adducts ‘anti’-11 and ‘anti’-12, respectively of 9 and of a third tricyclic intermediate 16 which is at 200° in thermal equilibrium with 9 and 10 (cf. Scheme 6). The heptalenedicarboxylates 5a and 5b as well as 6a and 6b are interconverting slowly already at ambient temperature (Scheme 4). The thermal reaction of guaiazulene (1) with excess ADM in decalin at 190° leads alongside with the known heptalene- (3a) and azulene-1,2-dicarboxylates (4; cf. Schemes 2 and 7) to the formation of six tetracyclic compounds ‘anti’-17 to ‘anti’-21 as well as ‘syn’-19 and small amounts of a 4:1 mixture of the tricyclic tetracarboxylates 22 and 23. The structure of the tetracyclic compounds can be traced back by a retro-Diels-Alder reaction to the corresponding structures of tricyclic compounds (24--29; cf. Scheme 8) which are thermally interconverting by [1,5]-C shifts at 190°. The tricyclic tetracarboxylates 22 and 23, which are slowly equilibrating already at ambient temperature, are formed by thermal addition of ADM to the seven-membered ring of dimethyl 5-isopropyl-3,8-dimethylazulene-1,2-dicarboxylate (7; cf. Scheme 10). Azulene 7 which is electronically deactivated by the two MeOCO groups at C(1) and C(2) shows no more thermal reactivity in the presence of ADM at the five-membered ring (cf. Scheme 11). The tricyclic tetracarboxylates 22 and 23 react with excess ADM at 200° in a slow Diels-Alder reaction to form the tetracyclic hexacarboxylates 32, ‘anti’-33, and ‘anti’-34 (cf. Schemes 10-12 as well as Scheme 13). A structural correlation of the tri- and tetracyclic compounds is only feasible if thermal equilibration via [1,5]-C shifts between all six possible tricyclic tetracarboxylates (22, 23, and 35-38; cf. Scheme 13) is assumed. The tetracyclic hexacarboxylates 32, ‘anti’-33, and ‘anti’-34 seem to arise from the most strained tricyclic intermediates (36-38) by the Diels-Alder reaction with ADM.

Notes: Syntheses of Phosphonic- and Phosphinic Analogues of Pantothenic Acid Ethyl Ester and of the Phosphonic Analogue of PantetheineThe replacement of amino acids in peptides by phosphono-analogous (aminoalkyl)phosphonic acids 1, (2-aminoethyl)phosphonic acid (2) and substituted derivatives has been an important aspect of peptides research in the last years. In pantothenic acid (3), there is a peptide linkage between (2R)-2,4-dihydroxy-3,3-dimethylbutyric acid and the amino group of β-alanine, and in pantetheine (4), there is a second peptide linkage between the β-alanine and cysteamine. The synthesis of phosphono and phosphino analogues of pantothenic acid ethyl ester, where the β-alanine is replaced by the diethyl ester of (2-aminoethyl)phosphonic acid and the ethyl ester of (2-aminoethyl)methylphosphonic acid, respectively, and the syntheses of the phosphono analogue of pantetheine, where the β-alanine is replaced by (2-aminoethyl)phosphonic acid, are described.

Notes: Heating diastereoisomerically pure N-acylsultams 3 or 4 with allyl alcohol/Ti(OR)4 efficiently yields sultams 1 or 2 and allyl esters 5. Esters 5 are hydrolyzed under nonbasic conditions in the presence of Wilkinson's catalyst to give enantiomerically and diastereoisomerically pure carboxylic acids 7. A series of [(fluoren-9-yl)methoxy]-carbonyl-(Fmoc)-protected amino acids 14 were thus prepared from N-[N'-(Fmoc)amino]acylsultams 12.

Notes: Glycosidation by the diazirine 1, the trichloroacetimidate 4, and the bromide 5 of the altro-diol 2, possessing an intramolecular H-bond (HO—C(3) to O—C(1)) in solution, but not in the solid state, proceeds with high and complementary regioselectivity. From 2 and 1, one obtains mostly the 1,2-linked disaccharides 10 and 11 (β-D 〉 α-D), together with the 1,3-linked isomers 12 and 13 (α-D 〉 β-D; 1,2-/1,3-linked products ca. 9:1), the demethylated 1,3-linked disaccharides 24-27, the trisaccharides 19-22, the lactone azines 23, and the hydroxyglucal 18, while 2 reacted with 4 or 5 to yield mostly the 1,3-linked disaccharides (1,2-/1,3-linked products ca. 1:9). The disaccharides were additionally characterized as acetates (→ 14-17, 28-31). Yields and stereoselectivity depended upon the donor, stoichiometry, solvent, temperature, and concentration. Glycosidation of the 1,3-linked disaccharides with 1 yielded the trisaccharides 19-22. Reaction of the β-D-altro-diol 3 with 1 gave the 1,2- and 1,3-linked disaccharides 32/33 and 34/35 in a 1:1 ratio, characterized as the acetates 36-39, while glycosidation with 5 according to Lemieux proceeded regioselectively (1,2-/1,3-linked products 91:9). The monotosylates 6 and 7 reacted with 1 to yield the anomeric pairs 40/41, and 42/43 of the tosylated disaccharides; the oxiranes 44 and 45 were not observed.

Notes: A wide range of cyclic and open-chain α,α-disubstituted α-amino acids 1a-p were prepared. The racemic N-acylated α,α-disubstituted amino acids were resolved by coupling to chiral amines 15-18 derived from (S)-phenylalanine to form diastereoisomers 19/20 or 21/22 that could be separated by crystallization and/or flash chromatography on silica gel (Scheme 3). Selective cleavage via the 1,3-oxazol-5(4H)-ones 10a-p gave the corresponding optically pure α,α-disubstituted amino-acid derivatives 11 or 12 in high yield (Scheme 3). The absolute configurations of the α,α-disubstituted amino acids were determined from X-ray structures of the diastereoisomers 20, 21g′, 22d.

Notes: The ligand 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (mbzimpy, 1) reacts with EuIII to give [Eu(mbzimpy)(NO3)3(CH3OH)] [4] whose crystal structure (EuC22H21N8O10, a = 7.658(3) Å, b = 19.136(2) Å, c = 8.882 Å, β = 104.07(1)°, monoclinic, P21, Z = 2) shows a mononuclear structure where EuIII is ten-coordinate by a meridional tridentate mbzimpy ligand, three bidentate nitrates, and one CH3OH molecule, leading to a low-symmetry coordination sphere around the metalion. Essentially the same coordination is found in the crystal structure of [Eu(obzimpy)(NO3)3] (8) (EuC35H45N8O9, a = 9.095(2) Å, b = 16.624(2) Å, c = 26.198(6) Å, β = 95.85(1)°, monoclinic, P21/c, Z = 4) obtained by reaction of 2,6-bis(1-octylbenzimidazol-2-yl)pyridine (obzimpy, 2) with EuIII. Detailed photophysical studies of crystalline [Ln(mbzimpy)(NO3)3(CH3OH)] and [Ln(obzimpy)(NO3)3] complexes (Ln = Eu, Gd, Tb, Lu) show that 1 and 2 display 1ππ* and 3ππ* excited states very similar to those observed in 2,2′:6′,2″-terpyridine, leading to efficient ligand to LnIII intramolecular energy transfer. Spectroscopic results show that an extremely efficient mbzimpy-to-EuIII transfer occurs in [Ln(mbzimpy)(NO3)3(CH3OH)] and in the case of TbIII, a TbIII-to-mbzimpy back transfer is also implied in the deactivation process. The origin of these peculiar effects and the influence of ligand design by going from mbzimpy to obzimpy are discussed. 1H-NMR and luminescence data indicate that the structure found in the crystal is essentially maintained in solution.

Notes: The key elements associated with the synthetic elaboration of functionalized trans-tricyclo-[9.3.1.03,8]pentadecanes carrying either a bridgehead H or OH substituent are detailed. Starting with 12, a ketone available in two steps from (R)-2-oxo-7,7-dimethyl-l-vinylbicyclo[2.2.1]heptane, it proved possible to introduce trans-B/C ring juncture configuration as in 16 in five steps. This advanced intermediate constitutes the point of bifurcation. The pathway to taxusin precursor 23 was attained by stereospecific osmylation, reduction, and pinacol-like 1,2-Wagner-Meerwein rearrangement within acetoxy mesylate 22c. Still more abbreviated is the route to 32, which again takes advantage of the osmylation step but proceeds, forward without reduction of the rear carbonyl group. Once hydroxy diketone 31 is produced, equilibration in the presence of (t-BuO)3Al results in complete conversion to 32. The many stereoselective transformations developed in the course of this study, in combination with the several thermodynamic questions that have been clarified, are expected to be highly serviceable as more advanced thrusts toward taxusin and taxol are mounted.

Notes: Synthesis of (±)-Muscopyridine via C-ZIP Ring EnlargementTreatment of 4-(1-nitro-2-oxocyclododec-1-yl)butanal (1) and of its methyl derivative 5 with pentylamine in EtOH at room temperature gave the ring-enlarged aminomethylidene derivatives 6 and 7, respectively (Scheme 1). After hydrolysis of the aminomethylidene group in 6 and 7 and deformylation followed by a reductive Nef-type reaction, the macrocyclic diketones 10 and 11, respectively, were obtained. They were transformed by a modified Hantzsch procedure to the title compound (±)-muscopyridine (13) and normuscopyridine (12), respectively.

Notes: Reaction of diphenyl phosphorochloridate with amide enolates and subsequent treatment with NaN3 leads to 2-monosubstituted 3-amino-2H -azirines 5 in moderate yields. The reactivity of these azirines is briefly explored.

Notes: The magnetic circular dichroism (MCD) and electronic absorption spectra of tropothione have been measured. The circular-dichroism (CD) spectrum of the β-cyclodextrin complex with tropothione is also reported. The absorption bands of tropothione are assigned.

Notes: Irradiation of newly synthesized 2,2-dimethyl-2,3-dihydro-4H-thiin-4-one (1) in furan affords the two [4 + 2] cycloadducts 3 and 4 and the [2 + 2] cycloadduct 5 in a 5:4:1 ratio (Scheme 1). Irradiation of 1 in MeOH gives a 3:2 mixture of 5- and 6-methoxy-2,2-dimethylthian-4-ones 6 and 7. Irradiation in CD3OD affords the same (deuterated) adducts with the CD3O and D groups trans to each other, results compatible with cis-addition of MeOH to a trans -configurated ground-state enone. Irradiation of the same enone in furan/MeOH 1:1 gives only the furan cycloadducts 3-5 and no MeOH adducts, suggesting that furan interacts with the (excited) triplet enone before the deactivation of this species to a ground-state (E)-cyclohexenone, which then reacts with MeOH. On irradiation in furan, the corresponding five-membered thiaenone, 2,2-dimethylthiophen-3(2H)-one (2) affords only one, cis-fused, [4 + 2] cycloadduct with ‘exo’-configuration, i.e. 8, and 2 does not undergo solvent addition but rather cyclodimerization (→9) on irradiation in MeOH (Scheme 1).

Notes: This paper marks the first reported detection of radical cations by Electrospray-Ionization Mass Spectrometry (ESI-MS). Electron Spin Resonance (ESR) measurements have proven that the detected radical cation existed already in solution and has not been generated by the electrospray ionization technique. However, we observed that the radical cation can be generated by changes in the ionization conditions. A molar mixture of 2-amino-5,6,7,8-tetrahydro-5-methylpterin-4(4H)-one dihydrochloride ( = 5,6,7,8-tetrahydro-N(5)-methylpterin-2 HCl, N(5)-MTHP-2 HCl), and tris(pentane-2,4-dionato)iron(III) in MeCN at pH 2-3 leads to the formation of a [bis(pentane-2,4-dionato)(2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (4H)-one)]iron complex ( = [bis(pentane-2,4-dionato) (5,6,7,8-tetrahydro-N(5)-methylpteridin)]iron complex) which can be detected by ESI-MS. The results suggest that this complex might be an FeII radical cation, which could possibly be a suitable model complex for the active center of the phenylalanine hydroxylase. In the same solution, the stable radical cation of N(5)-MTHP is identified by ESI-MS and ESR.

Notes: Glycosidation of the myo-inositol derivatives 2 and 3 by the diazirine 1 yields 90% of a diastereoisomer pair of β-D-glycosides in a 1:1 ratio, i.e. 5/6 and 7/8, respectively (Scheme 1). The crystal structure of 3 shows a strong intramolecular H-bond, which persists in solution, as indicated by FT-IR and 1H-NMR spectra. Yields and diastereoselectivity are lower for the glycosidation of 24 by 1 (Scheme 3). The resulting 1,2- and 1,4-linked disaccharides 25-28 were isolated as their acetates 29-32. The previously determined crystal structure of 24 shows no intramolecular H-bonds. The yield of the glycosidation of 24, but not of 3, depends upon the concentration, indicating that activation of 24 by intermolecular H-bonds is required. Glycosidation of 2 and 3 with the trichloroacetimidate 14 gave mixtures of four (5,6,15, and 16), and six (7,8, and 17-20) disaccharides, respectively (Scheme 2).

Notes: Dimethyl azulene-1,2-dicarboxylates are reduced with a 4-5 molar excess of DIBAH in Et2O/hexane at 0° to yield the corresponding 2-(hydroxymethyl)-1-methylazulenes which can be further reduced to 1,2-dimethylazulenes on treatment with Et3SiH in TFA at 60° (cf. the Table).

Notes: The reaction of dodecacarbonyltriruthenium with 1,3,5-trithiacyclohexane (1,3,5-trithiane) in refluxing THF yields [Ru3(CO)6(μ2-CO)3{μ3-(η3-C3S3H6)}] (1) in which the three S-atoms of the cyclic ligand coordinate to the three Ru-atoms of the metal core. X-Ray diffraction reveals a nearly perfect C3v symmetry for the molecule. The variable-temperature 13C-NMR spectra show the carbonyl ligands to be fluxional in solution.

Notes: The complexes [Fe(tdci)2]Cl3 and [Al(tdci)2]Cl3 (tdci = 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol) were prepared and characterized by mass spectrometry, NMR spectroscopy, and magnetic-susceptibility measurements. The formation constants were determined in aqueous solution (25°, 0.1M KCl) by potentiometric titration. pK values of H3(tdci)3+: 5.89, 7.62, 9.68; FeIII complexes: log βML = 18.8, log βML2 = 32.6; AlIII complexes: log βML = 14.3, logβML2 = 26.4. The protonated complex [FeH(tdci)2]4+ has also been identified. In contrast to the high stability of the FeIII and AlIII complexes, only weak interactions of tdci with CuII have been observed in aqueous solution (25°, 0.1M KNO3).

Notes: 2-Monosubstituted 3-amino-2H-azirines 2 react with several heterocycles containing acidic NH groups via ring expansions, leading to benzo[g][1,2,5]thiadiazocin 1,1-dioxide derivatives 6 and imidazoles 9, 10, and 13, respectively.

Notes: Oligonucleotides containing 2′-deoxyisoguanosine (1) or 2-chloro-2′-deoxyadenosine (2a) have been prepared by solid-phase synthesis. Suitably protected phosphonates 3a, 4a, and 4b as well as the phosphoramidite of 1 have been obtained from the nucleosides 1, 2a, or 2b via the (dimethylamino)methylidene derivatives 5-7. 4,4′-Dimethoxytrityl groups were introduced to yield the base-protected derivatives 8-10. Alternatively to the direct incorporation of 1 into oligonucleotides, they were also obtained by the photochemical conversion of a 2a residue within the oligonucleotide chain.

Notes: Seven redox stages, the dication 12+, the radical cation \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document}, the neutral 1, the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, the dianion 12-, the radical trianion \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document}, and the tetraanion 14-, are indicated by cyclic voltammetry for the bisphane 1, in which the benzene decks of two lateral paracyclophane moieties are orthogonal to the plane of anthracene framework. In \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, the unpaired electron is accommodated into the central anthracene subsystem, and the same statement holds for the two positive or negative charges in 12+ and 12-. Formation of \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document} and 1- occurs through admission of additional electrons one-by-one into the two paracyclophane moieties flanking the doubly charged anthracene subsystem in 12-. The above-postulated, successive release or uptake of electrons by the individual parts of the bisphane is in perfect accord with the hyperfine data determined by ESR and ENDOR spectroscopy for \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document}, as well as for radical ions of suitable reference compounds.

Notes: Hydroboration of aliphatic 1-alkynes with freshly prepared dicyclohexylborane (1 mol-equiv., hexane), treatment of the resulting [(E)-1-alkenyl]boranes 5 with Et2Zn or Me2Zn (1.05 mol-equiv.) followed by addition of (-)-3-exo-(dimethylamino)isoborneol (DAIB, 8; 0.01 mol-equiv.), subsequent addition of a solution of an aromatic or aliphatic aldehyde (1 mol-equiv., hexane), and quenching with aq. NH4Cl provided (E)-allyl alcohols 6 usually in 70-95% yield with 79-98% enantiomeric excess (Scheme 3 and Table).

Notes: Synthesis of Macrocyles by Ring Enlargement of 14-Membered Cyclic ImidesIn the presence of a base, cyclododecanone derivative 2, activated in α-position by an allyloxycarbonyl group, underwent ring enlargement with isocyanates to give 14-membered imides (Schemes 1-3). Cleavage of the activating group gave new 14-membered imides which could be transformed by further ring-enlargement reactions into new macrocyclic compounds.

Notes: The photolyses and thermolyses of the α,β-epoxy silyl ketones 5 and 6 are described. On n,π*-excitation, the silyl ketones 5 and 6 were transformed to the ketone 7 and the ketene 8 in quantitative yield. The formation of 8 may be explained by initial cleavage of the C(α)—O bond and subsequent C(1)→C(2) migration of the (t-Bu)Me2Si group. In contrast to the acylsilanes 5 and 6, the photolyses of the analogous methyl ketones 11 and 12 gave a very complex mixture of products. On thermolysis, 5 and 6 yielded the ketone 7 and the acetylenic compound 9, which were probably formed via a siloxycarbene intermediate. In addition, the 1,3-dioxle 10 was formed via an initial C(α)—C(β) bond cleavage leading to the ylide g and subsequent intramolecular addition of the carbonyl group. The analogous 1,3-dioxole 13 was obtained on pyrolysis of the methyl ketones 11 and 12.

Notes: Results are reported for high-energy beam experiments which establish the formation of endohedral carbon cluster-noble gas compounds by bimolecular reactions of Cxn+ (x = 60, 70; n = 1, 2, 3) with He and C60+· with Ne. The ions were accelerated up to 8 ke V in a four-sector mass spectrometer and allowed to collide with the noble gas in a collision chamber at room temperatur. Product ions were monitored with a B/E = constant linked scan. Within the sensivity of the experiments, no carbon cluster-gas compounds were observed in the reactions of C60+· with H2, D2, O2, Ar, and SF6, or of C70+· with O2. The observed fall in the cross-section for carbon cluster-noble gas compounds with increasing size of the noble gas, the observation of unimolecular loss of C2 from mass-selected CxHe+ ions, and the elimination of carbon fragments instead of He observed in the formation of the collision-induced CxHen+ product ions are taken as evidence for endohedral compound formation. Results of ab initio molecular-orbital calculations for the perpendicular penetration of the plane of ionized benzene with He, Ne, and Ar indicate that sufficient kinetic energy should be available in the collisions with C60+· to penetrate the C60+· cage at the collision energies of the experiments.

Notes: Chiral acylnitroso dienophiles 14, which were obtained from L-proline and from D-mandelic acid, reacted with cyclohexa-1,3-diene to give the expected diastereoisomers 15 and 16 (Scheme 2 and Table 1). The d.e. values for these Diels-Alder reactions were moderate; they are related to the molecular stiffness of the dienophiles. The absolute configuration of the major cycloadducts was interpreted in terms of HOMO/LUMO interactions, the approach being ‘endo’ and the acylintroso dienophiles reacting from their s-cis-conformation.

Notes: The synthesis and properties of the molecular reduction device 7b (CoII-V5++) consisting of a reduction catalyst (a derivative of vitamin B12, CoII) and a covalently linked 10-electron reservoir (five viologen units, V++) is described. The five viologen subunits were introduced at C(2) and C(3) of the side chains c and g and b, e and f, respectively, of an appropriate derivative of heptamethyl cob(III)yrinate by N-alkylation of 1-methyl-4,4′-bipyridinium iodide (see Scheme). The pentaviologen-linked corrinatocobalt(II) complex 7b behaves as a molecular electron trap with respect to the CoIII/CoII redox couple. The phenomenon is related to the structural and thermodynamic relation of the corrin and viologen subunits in 7b, i.e. the relative redoc energies and the spherical inner-outer arrangement of the types of redox systems. When completely reduced to CoI-V50, 7b exhibits multiple reductive elimination of trans-1,2-dibromocyclohexane to cyclohexene under concomitant oxidation to CoII-V5++. Rate measurements indicate that the reduction occurs via CoI which is regenerated by intramolecular electron transfer from the periphery of the molecule, i.e. by V0 and V++.

Notes: [(1,3-Dioxolan-2-ylidene)methyl]phosphonates and -phosphinates as [simple] Synthons in Heterocyclic SynthesisThe readily available [(1,3-dioxolane-2-ylidene)methyl]phosphonates and -phosphinates 2a-f (Scheme 1) can be transformed with amines to aliphatic ketene N,O-and N,N-acetales (see Scheme 2, 2a → 3-7). Alkanediamines yield with 2a-f the imidazolidines 8a-f and the hexahydropyrimidines 9a-d (Scheme 3). the oxazolidine derivatives 10a-e and the thiazolidine 11 are accessible under special reaction conditions starting from 2a, b (Scheme 4). Hydrazines react with the CN-group-containing ketene O,O-acetals 2a-c to the pyrazoles 12a-g, whereof 12a, d, e can be cyclized to pyrazolo[1,5-a]pyrimidines 13a-d (Scheme 5). Amidines as starting materials transform 2a-c in an analogous way to the pyrimidine derivatives 14a-c (Scheme 6).

Notes: A stereodivergent synthesis of enantiomerically pure E-nor-15-azayohimbines via condensation of tryptamine with derivatives of pyroglutamate 4 is reported. When the Pictet-Spengler reaction was induced in refluxing aqueous AcOH a nearly equimolar ratio of lactams 7 and 8 was obtained, whereas under kinetic control (TFA, room temperature) the trans-derivative 8 was the major product. In contrast, cyclization of amido acetal 12 with TsOH gave the cis-derivative 7 as preponderant component.

Notes: The 4,4′,6,6′-tetrasubstituted 2,2′-alkylidenebis(phenols) 1 reacted with CISCOI to give spiro[1,3-benzoxathiepin-4(5H), 1′-cyclohexa[2,4]diene]-2,2′-diones 4, together with cyclic carbonates 5. The structures of the products were elucidated mainly by 13C-NMR and 1H-NMR spectroscopy.

Notes: Heterocycles Starting from Bis(alkoxycarbonyl)ketene Ethylene Acetals ( = Dialkyl 2-(1,3-Dioxolan-2-ylidene)propane-1,3-dioate). Synthesis and Properties of a New Class of Pyrazolium BetainesThe readily available bis(alkoxycarbonyl)ketene ethylene acetals 1 react with bifunctional nucleophiles to give heterocycles 2-5 (Scheme 1). Their reactions with N,N-dialkylhydrazines lead to the pyrazolium betaines 7a-f (Scheme 4). Cyclic N,N-dialkylhydrazines give spiro compounds 7d-f. The reaction of thioketene acetal 12 and of the derivative 15 of methanetricarboxylic acid with N,N-dimethylhydrazine results in the formation of 3-(methylthio)- and 3-methoxypyrazolium betaine 7g and 7h, respectively (Scheme 4). The chemical reactivity of the synthesized pyrazolium betaines 7 was tested. The structure of the 3-(methylthio) derivative 7g was determined by X-ray analysis.

Notes: Strong dienophiles prefer to add onto the diene moiety attached at C(2),C(3) of 2,3,6,7-tetramethylidenebicyclo[3.2.1]octane ((±)-1; see Scheme 1), whereas in the case of 3,4,6,7-tetramethylidenebicyclo[3.2.1]octane-2-exo,8-syn-diyl derivatives, the diene moiety at C(6),C(7) reacts faster than that at C(3),C(4), as long the bulk of the 8-syn-substituent is large enough (see Schemes 2 and 3).

Notes: On reaction with ‘O’-donors or O2, the synthetic P-450 analogue 2 undergoes O-insertion at a nonactivated C—H bond of the covalently bound substrate. The mechanism of O-insertion with O2 most likely involves homolytic cleavage of the O—O bond followed by O-insertion via radical recombination.

Notes: In π systems with localized double bonds, the switch from one localization pattern to another symmetry-equivalent one, and the corresponding changes in electron distribution are often considered to proceed via a delocalized transition state of higher symmetry. We present a different mechanism, according to which the double-bond localization and the concomitant charge distributions can fluctuate without change in energy and without passing through a delocalized, higher-symmetry transition state. This result is obtained within a simple, independent-electron (HMO-type) treatment.

Notes: Acid-catalyzed cyclizations under thermodynamically and kinetically controlled conditions of the hydroxyenol ethers 18-21 are reported. Thermodynamically controlled cyclizations of 18, 19 and 21 produced only the more stable corresponding spiroacetals 22 and 27. Thermodynamically controlled cyclization of compound 20 produced a 1:1 mixture of non-epimerisable spiroacetals 24 and 26. On the other hand, kinetically controlled cyclizations of the same four hydroxyenol ethers produced, along with the more stable spiroacetals mentioned above, the less stable spiroacetals 23, 25, and 28. These results show that the kinetically controlled cyclization takes place via an early transition state which produces a mixture of the less stable and the more stable isomers. These results are explained by an early transition state taking into account the principle of stereoelectronic control while following the antiperiplanar lone-pair hypothesis (Bürgi-Dunitz angle of attack of a nucleophile on a π system).

Notes: Chiral enolates 5 and 10, generated by radical addition and subsequent reduction, show diastereofacial selectivity during protonation. In the presence of substituted amines, diastereoselectivity is enhanced and becomes comparable to radical stereoselection. Diastereoselectivities up to 99:1 and yields up to 90% are reached.

Notes: The syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pKHA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH2Cl2 at room temperature leads to the glycosides 2-5 in yields between 60 and 34% (Scheme 1 and Table 1). At -70 to -60°, yields are markedly higher. In CH2Cl2, diastereoselectivities are very low. In THF, at -70 to -60°, however, glycosidation of i-PrOH leads to α-D-/β-D-4 in a ratio of 8:92. More strongly acidic alcohols, such as CF3CH2OH, (CF3)2 CHOH, and (CF3)2C(Me)OH, and the highly fluorinated long-chain alcohols CF3(CF2)5(CH2)2OH (11) and CHF2(CF2)9CH2OH (13) react (CH2Cl2, r.t.) in yields between 73 and 85% and lead mainly to the β-D-glucosides β-D-6 to β-D-8, β-D-12, and β-D-14 (d.e. 14-68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimetoxyethane, or THF are used, as examined for the glycosidation of (CF3)2C(Me)OH, yielding (1,2-dimethoxyethane, 25°) 80% of α-D-/ β-D-8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF3)2C(Me)OH yields up to 55% of the imidate 10. Glycosidation of di-O-isopropylideneglucose 15 leads to 16 (CH2Cl2, r.t.; 65%, α-D/ β-D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10, derived from the attack of (CF3)2MeCO- on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α-D-9 and β-D-9, derived by attack of i-PrO- on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO—C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO- in the π plane of the (solvated) oxonium ion.

Notes: The green seaweed Caulerpa taxifolia (VAHL) C. AGARDH (Caulerpales), which, after its recent accidental introduction, is growing in the region of Cap Martin much more vigorously than in the tropics, is shown to contain the known sesquiterpenic toxins caulerpenyne (1) - in larger amounts than in tropical Caulerpales - and oxytoxin 1 (2). Novel, potentially toxic products isolated in small amounts from this seaweed include the sesquiterpenes taxifolial A ( = (5E)-6,10-dimethyl-2-[(E)2-oxoethylidene]undeca-5,9-dien-7- yne-1,3-diyl diacetate; 3), taxifolial B (= (1E,6E,10E)-3-[(Z)-acetoxymethylidene]-7, 11-dimethyl-12-oxododeca-1,6,10-trien-8-yne-1,4-diyl diacetate; 4), 10,11-epoxycaulerpenyne ( = (1E,6E)-3-[(Z)-acetoxymethylidene]-10,11-epoxy-7, 11-dimethyldodeca-1,6-dien-8-yne-1,4-diyl diacetate; 1:1 diastereoisomer mixture; 5), and taxifolial C ( = (2Z,6E)-3-formyl-7,11-dimethyldodeca-2,6,10-trien-8-yne-1,1, 4-triyl triacetate; 6), besides, as the first example of a monoterpene from the Caulerpales, taxifolial D ( = (2Z)-3,7-dimethylocta-2, 6-dien-4-ynal; 7).

Notes: The synthesis of two series of cyclometalated RhIII compounds is described, namely of 5 dinuclear chlorobridged species [{Rh(C⁁N)2} (μ-Cl)2] A and of 15 mononuclear complexes [Rh(C⁁N)2(N⁁N)]+ B; C⁁N stands for five different cyclometalating ligands, i.e. deprotonated phenylpyridine, deprotonated 2-(thienyl)pyridine, and three deprotonated 1-aryl-1H-pyrazoles, and N⁁N for six diimine ligands such as 2,2-bihyridine, 2,2′-bi-1H-imidazole, and 2,2′-bipyrimidine. For (2,2′-bipyridine)bis[2-(thien-2-yl)pyridinato-N,C3′]rhodium(III) chloride, an X-ray structure determination was carried out. In the other cases, 1H-NMR spectra established the configuration of the complexes. All mononuclear and dinuclear complexes show a C,C cis-configuration. The UV/VIS-absorption bands at longest wavelength are most likely due to metal-to-ligand charge-transfer (MLCT) transitions, depending on the nature of the cyclometalating ligand C⁁N and on the diimine ligand N⁁N. The receptor orbital is in some cases on the cyclometalating ligand, in others on the diimine. All monomer complexes exhibit at least one reversible reduction wave in the cyclovoltammogram in dimethylformamide solutions, attributable to a ligand-centered reduction. It is, therefore, concluded that the LUMO in [Rh(C⁁N)2(N⁁N)]+ is of L(π*) character, as opposed to [Rh(bpy)3]3+, where it is a metal d-orbital. The crystal system of (2,2′-bipyridine)bis[2-(thien-2-yl)pyridinato-N,C3′]rhodium(III) chloride - water (1/2.125) is tetragonal (space group P4; R = 0.036, Rw = 0.040). The Rh-atom has slightly distorted octahedral environment; the average distances are (Rh—N/thienyl—pyridine) = 2.060 (3), Rh—C = 1.9885 (3), and Rh—N(bipyridine) = 2.1415 (3) Å. Of the three ligands the 2,2′-bipyridine is the most planar.

Notes: The previously prepared disaccharide 2 was deprotected (→3) and transformed into the trichloroacetimidate 4. In the presence of Me3SiOTf, 4 reacted regioselectively with the racemic allosamizoline benzyl ether 5, to yield (61%) the pseudotrisaccharides 7-10 (44:40:9:7) and the elimination product 6 (Scheme 1). Selective dephthaloylation (MeNH2, MeOH) of 7 and 8, followed by acetylation, gave 12 (73%) and 13 (74%), respectively (Scheme 2); harsher conditions (NH2NH2.H2O, EtOH, reflux), followed by acetylation, transformed 7 into 11. Deacetylation of 11-13 yielded 14-16, respectively. Allosamidin (1) was obtained in high yield by hydrogenation of 15 under acidic conditions (Scheme 3). Similarly, 16 and 14 were transformed into 17 and 18, respectively. Preliminary data on the inhibition of endochitinases by 1 and 17 are reported.

Notes: In connection with structure-activity relationship studies, analogues of campholenal ((+)-4b), an important building block for sandalwood-like odorants, were prepared. The five-membered-ring analogues 4 were obtained by epoxidation of the corresponding α-pinene derivatives 2, followed by catalytic ZnBr2 isomerisation (Scheme 2). The six-membered-ring skeleton was obtained by ozonolysis of α-campholenyl acetate ((-)-14b), followed by intramolecular aldol condensation (Scheme 5). 13C-NMR assignments are given.

Notes: The crystal structure of 2-acetamido-1,5-anhydro-1-azi-3-O-benzyl-4,6-O-benzylidene-1,2- dideoxy-D-allitol (6) is reported, and the structural parameters of the diazirine moiety are compared with those of other free diazirines for which structural information has been determined or calculated previously. Lengthening of the N=N bond and shortening of the C—N bonds can be observed as the substituents at the C-atom of the diazirine ring become more electronegative and/or stronger π-electron donors. This is consistent with descriptions of the bonding nature of diazirines and similar observations made on substituted cyclopropanes.