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Conformations of the 10‐membered Ring in 5, 10‐Secosteroids. II . ( E )‐3α‐Acetoxy‐5, 10‐ seco ‐1 (10)‐cholesten‐5‐one and ( E )‐5, 10‐ seco ‐1 (10)‐cholestene‐3, 5‐dione
Author(s) -
Fuhrer Hermann,
Lorenc Ljubinka,
Pavlović Vladimir,
Rihs Grety,
Rist Günther,
Kalvoda Jaroslav,
Mihailović Mihailo Lj.
Publication year - 1979
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19790620610
Subject(s) - chemistry , ring (chemistry) , toluene , stereochemistry , nmr spectra database , conformational isomerism , cyclohexane conformation , oxime , spectral line , molecule , medicinal chemistry , organic chemistry , hydrogen bond , physics , astronomy
( E )‐3α‐Acetoxy‐5, 10‐ seco ‐1(10)‐cholesten‐5‐one ( 3 ) was synthesized by fragmentation of 3α‐acetoxy‐5α‐cholestan‐5‐ol ( 1 ) using the photochemical version [3] of the lead tetraacetate reaction [4], and transformed into the corresponding 3‐oxo‐compound ( 5 ). Two conformations ( A 2 αand B 1 α ) were deduced for the 10‐membered ring of 3 by analysis of the 1 H‐ and 13 C‐NMR. spectra in toluene. The major conformation ( A 2 α ) corresponds to that found in the solid state by X‐ray analysis. According to its NMR. spectra in toluene, the medium‐sized ring of the diketone 5 exists also predominantly in two conformations, the major one being analogous to A 1 β(the solid‐state conformation of the 3β‐acetoxy isomer ( 9 ) [1]) and the minor one to A 2 α(see above). The stereochemistry of the acidcatalyzed and thermal cyclisations of 3 as well as of the corresponding 5‐oxime is discussed in terms of conformational factors.