Preparation and Solvolysis of Epi-ψ-cholesterol

Enantiospecific First Total Synthesis and Assignment of Absolute Configuration of the Sesquiterpene (−)-Cucumin H

“…Introduction of the gem -dimethyl group by one-step double alkylation transformed enone 22 into enone 25 containing the complete carbon framework of ceratopicanes. Allylic oxidation of enone 25 with di- tert -butyl chromate furnished enedione 26 in a highly regioselective manner. , Regio- and stereoselective reduction of enedione 26 with sodium borohydride−cerium chloride heptahydrate furnished alcohol 27 , which is isomeric to cucumin H ( 8 ). To unambiguously establish the stereochemistry of alcohol in 27 , it was converted into p -nitrobenzoate 28 employing a Mitsunobu inversion .…”

The Oxidation of Some Steroidal Dienes and Trienes with Chromic Acid

“…The oxidation of steroidal alkenes by chromic acid 1 or by reagents derived from chromium trioxide such as chromyl diacetate, 2 di-tert-butoxychromate, 3 pyridinium chlorochromate, 4Y5 pyridinium dichromate 6 or the chromium trioxide^pyrazole complex 7 may yield products arising from addition to the alkene such as epoxides and their cleavage products or from allylic oxidation. However the oxidation of steroidal dienes has been less widely investigated.…”

An Investigation of Anchimeric Assistance in Certain Homoallylic Alcohols

“…3a~°i /'-Cholesteryl p-toluenesulfonate (III) fails to give indication of anchimeric assistance upon undergoing solvolysis, although the ester group is equatorial and seemingly properly situated for participation. 4a 'b This result has been explained in terms of the rigidity of the B-ring, due to the trans B/Cring fusion.41 --cholesteryl p-toluenesulfonate also fails to exhibit homoallylic participation.4 5 While these results indicate that definite geometric requirements must be met in order for such participation to occur, it is possible to have some deviation from the basic cholesterol structure and still observe a significant amount of homoallylic participation, for B-norcholesteryl p-toluenesulfonate (IV) does solvolyze with anchimeric assistance of the double bond at a rate one-half that of cholesteryl p-toluenesulfonate to yield 3,5-cyclo-Bnorcholesterol (V). 6 Consideration of the above-mentioned facts led to the decision that a study of the rates of solvolysis of the p-toluenesulfonates of certain bicyclic alcohols which contain the essential homoallylic structural features of cholesterol, but which lack the C and D rings (represented by figure VI) would be instructive.…”