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Intramolecular hydrogen bonding and structure of stereoisomeric 20(22)-hydroxy-22(23)-isoxazolinyl steroids

“…For the major 20-hydroxy-23-isoxazolinyl steroid stereoisomer 7b, characteristic features include a broader intense band for bound OH groups at 3560 cm -1 and a weak band for free hydroxyl groups at 3625 cm -1 , while for its minor stereoisomer 8b we see a band for free OH groups at 3640 cm -1 with a shoulder at 3620 cm -1 and a weak band for bound OH groups at 3565 cm -1 (curves 3 and 4). The major 22-hydroxy-23-isoxazolinyl steroid stereoisomers 9c, 12c and their minor stereoisomers 10c, 11c look the same spectroscopically: in the spectra of the first two, we observe a broad band at 3590 cm -1 (curves 5, 7), while in the spectra of the second two we observe a doublet band with maxima at 3605 cm -1 and 3630 cm -1 (curves 6,8).…”

“…As we see from examination of molecular models of the conformers, approach of the OH group to the C 24 atom is hindered by its pseudoaxial hydrogen atom, which "divides" the hydroxyl groups into equal sets occupying the sectors of the corresponding rotamers B and C. In this case, the OH groups delimited by the C 22 -C 23 bond and this hydrogen atom form an intramolecular hydrogen bond, while the OH groups located between the C 22 -H and C 24 -H bonds in the bB conformer of stereoisomer 10c and between the C 20 -C 22 and C 24 -H bonds in the a 2 C conformer of stereoisomer 11c remain free. Based on the relatively small shift ∆ν(OH) and the narrow shape of the band for bound OH groups in the spectra of the minor stereoisomers (curves 6,8), compared with these parameters in the spectra of the major stereoisomers (curves 5, 7), we may say that formation of weaker intramolecular OH...C hydrogen bonds occurs at greater interatomic distances than for the intramolecular OH...O hydrogen bonds.…”

Rearrangement of 2,3-Epoxy Alcohol Dimethylthiocarbamate Derivatives. Synthesis of 2,3-Epithio Alcohol Derivatives under Mild Conditions

“…Finally, the epoxy alcohols 24 and 25 (Scheme ), prepared from known 16α,17α-epoxy-3β-hydroxypregn-5-en-20-one 23 using the standard procedures, were examined. Alcohol 24 was transformed as described above into thiocarbamate 26 that was stable on storage and could be recovered unchanged after heating in refluxing toluene for a few hours.…”

Stereochemical assignments of 22-isoxazolinylsteroids using circular dichroism

“…Table 1 gives the measured CD and absorption spectra of the compounds. The studied 22-isoxazolinylsteroids were synthesized according to the published method [2][3][4]. …”