ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
(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 (A2α and B1α) were deduced for the 10-membered ring of 3 by analysis of the 1H- and 13C-NMR. spectra in toluene. The major conformation (A2α) 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 A1β (the solid-state conformation of the 3β-acetoxy isomer (9) [1]) and the minor one to A2α (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.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19790620610