STEROIDAL CYCLOBUTANONES, .3. THE SYNTHESIS AND STEREOCHEMISTRY OF 3-SPIRO-5-ALPHA-CHOLESTANE DERIVATIVES WITH 3-MEMBERED, 4-MEMBERED, AND 5-MEMBERED CARBON RINGS A DOUBLE CINE SUBSTITUTION IN SPIRO-ALPHA,ALPHA-DICHLOROCYCLOBUTAN-3-ONES

Diastereomeric [(3S)-5alpha]- and dichlorospiro-[cholestane-3,1'-cyclo butan]-3'-ones (1 and 2), prepared by cycloaddition reaction of dichlo roketene with 3-methylene-5alpha-cholestane, served as starting materi al for the synthesis of the related spirane derivatives. Thus, the syn thesis of spirocyclopentane (3-6), spirocyclobutane (9, 11, 13, 17-20) and spirocyclopropane steroids (12, 14, 15) is described. The sterica lly dependent reaction of spiro-alpha,alpha-dichlorocyclobutan-3-ones with an excess of sodium methanolate in methanol is reported. Thus, th e reaction of 1 with sodium methanolate gives 9, the product of the do uble cine substitution, while the corresponding reaction of compound 2 , which is sterically more hindered for similar nucleophilic attack, g ives mainly the spirocyclopropane 12. The stereochemistry of the spiro compounds is assigned on the basis of H-1- and C-13-NMR spectra.