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The utilisability of the photochemical oxygenation of Δ3,5-enol ethers of the type III is limited in 11β-hydroxy derivatives which under the conditions of enol-etherification undergo dehydration to a considerable extent. A method for the protection of the 11β-hydroxy group in the form of a 11-keto group has been elaborated; after the enol-etherification the keto group can be reduced back to the 11β-hydroxy group. more...

Infrared spectra of the L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured. Amides I-IV are not self associated in tetrachlormethane in the concentration 2 . 10-5 mol l-1 at room temperature and in tetrachloroethylene in the concentration 1.5 . 10-4 mol l-1 at temperatures above 65° C. True conformational changes are observable only with the least flexible amide IV which exists at room temperature in a C5 conformation. This conformational type is also highly populated in the valine derivative III, but is less important in the alanine and leucine derivatives I and II in which the intramolecularly bonded C7 and the distorted hydrogen-nonbonded conformations contribute seriously. more...

α-Amino-γ-bromobutyric acid and its derivatives were utilized in the preparation of some non-coded (non-proteinogenic) amino acids and their derivatives. The bromine atom was replaced by hydrogen, hydroxyl, iodine and nitro, amino, and thiocyanato groups. Homolanthionine was prepared by two methods. Homoserine has been shown to exist in three crystalline modifications whose differences in the IR spectra indicate conformational changes. more...

Substituted 2-bromo-1-phenylglyoxal 2-phenylhydrazones IIIa-f exist in tetrachloromethane or benzene solutions prevailingly in E-configuration and in conformation A with an intramolecular hydrogen bond. The latter was evidenced by the N-H valence frequency at 3 290 cm-1 and by 1H NMR shifts with reference to derivatives without a carbonyl group - α-chlorobenzaldehyde phenylhydrazones V. From dipole moments of IIIa-d, measured in benzene solution, the contribution of the hydrogen bond (μH) was evaluated to 17 . 10-30 C m. This quantity is twice larger than in any other reported compound but the direction of the vector is as usual: approximately from H to N. In structurally similar derivatives of hydroxylamine, substituted 2-phenylglyoxylhydroximoyl chlorides IVa-d, no intramolecular hydrogen bond was detected; the dipole moments found were interpreted in terms of the Z-configuration and the prevailing conformation G. more...

The protected 20(21)-en-20-ol ether III was oxidized with N-methylmorpholine N-oxide monohydrate and osmium tetroxide to give the hydroxy ketone IV which was converted into the bromo derivative VIII via the mesylate VI. Hantzsch reaction of the bromo ketone VIII with ethyl thioxamate afforded the thiazole XI whose hemisuccinate XIII and glycoside XV were prepared. more...

The synthesis of epimeric bromo ketones VII, VIII, XXV and XXVI, derived from 4,4-dimethyl-A-homo-4a-cholesten-3-one (I) and 4,4-dimethyl-A-homo-5-cholesten-3-one (XIII) is described in this paper. In the case of bromo ketones VII, VIII and XXV the IR data demonstrate the presence of conformers both with a quasi-axial and a quasi-equatorial bromine atom in the equilibrium mixture, the quasi-equatorial conformer being the predominant component. On the basis of IR, CD and 1H-NMR data the conformation of the ring A in compounds VII, VIII, XXV and XXVI is discussed. more...

Acid-catalyzed intramolecular cyclization of 6,7-dihydroxy-3α,5-cyclo-6,7-seco-5α-androstan-17-one (VII), 5,7-dihydroxy-3,5-methylene-5,7-secoandrostan-17-one and 5,7-dihydroxy-3β,5-cyclo-5,7-seco-A-homo-5β-androstan-17-one (XIII) in benzene and dioxane was investigated. The main cyclization products were 3,5-methylene-6-oxaandrostan-17-one (I) and/or 3β,5-cyclo-6-oxa-A-homo-5β-androstan-17-one (VIII). In the case of VI and VII the ratio of I and VIII was solvent-dependent: in benzene more VIII was formed than in dioxane. The mass spectra of I and VIII were almost identical and corresponded to the structure VIII. more...

Synthesis of the title optically active bicyclic dilactams I and II with cis- and trans-annelation of rings is described. The stereospecific synthesis started from (2R)-2-benzamido-2-(4-oxocyclohexyl)acetic acid ((-)-VI) whose absolute configuration was determined by chemical correlation with the known (2R)-2-amino-(4-hydroxyphenyl)acetic acid ((-)-IIIb). Relative configuration at the bridgehead atoms in I and II was assigned by 1H and 13C NMR spectroscopy and confirmed by X-ray diffraction analysis which showed the detailed conformation in crystal. According to the 1H NMR spectra in solution the trans-isomer II has the same configuration as in crystal whereas the cis-isomer I exists in two forms one of which is identical with that in crystal. This conformational analysis agrees also with the IR spectra, detecting an intramolecularly hydrogen-bonded conformation for IIbut no hydrogen bond for I. The CD spectra of both lactams were successfully interpreted using the exciton theory in the π-π region where it reflects the differences in the angles Φ and ψ (for I Φ = 110°, ψ = -143°; forII Φ = -145°, ψ = 162°). In the n-π transition region the interpretation was based on the quadrant rule and also inherent non-planarity of one of the amide groups in II. more...

Action of strongly basic reagents on methyl Nα-benzyloxycarbonylamino-γ-bromobutyrate leads to 1-aminocyclopropanecarboxylic acid derivatives whose structure was determined by 1H NMR, 13C NMR and IR spectroscopy. According to IR spectroscopy, the urethane CO-NH group in crystalline methyl 1-benzyloxycarbonylaminocyclopropanecarboxylate exists in the cis(E) conformation which on dissolution is transformed into the trans(Z) form. NMR spectroscopy showed that the acid-catalyzed esterification of α-amino-γ-bromobutyric acid is accompanied by replacement of the covalently bonded bromine by chlorine. more...