Steroidal cyclobutanones, I. Synthesis and stereochemistry of steroidal spirocyclobutanones

Abstract

Cycloaddition of dichloroketene to 3‐, 7‐, and 17‐methylene steroids affords the corresponding spirodichlorocyclobutanones, which can be reduced to monochloro‐ and unsubstituted spirocyclobutanones. Selective cycloaddition to the exo‐double bond is observed in the reaction of 3β‐acetoxy‐17‐methylene‐5‐androstene. The stereochemistry of spiro compounds is assigned on the basis of 1H‐ and 13C‐NMR spectra. Some steroidal spirolactones are obtained and their stereochemistry is assigned.

Cyclobutanone Approach to the Synthesis of Cardenolides

“…After chromatographic purification the reaction afforded dichlorocyclobutanone 7 in 58% isolated yield. We have previously found that purification of the crude reaction product on a SiO 2 column is usually accompanied by slow decomposition of the dichlorcyclobutanones 17b. The dichlorocyclobutanone 7 had spectral characteristics (IR, 1 H and 13 C NMR, MS) in accordance with the proposed structure.…”

“…The organic layer was dried with magnesium sulfate and the solvent was removed in vacuo. The residue was purified by chromatography on silica gel with benzene as eluent to give compound 7 (156 mg, 58%, slowly decomposed17b on silica gel) as an oil; two diastereoisomers were formed in a 2:1 ratio, as estimated from the integration of the signals at δ = 0.78 and 0.72 ppm in the 1 H NMR spectrum of the crude product. IR: $\tilde {\nu}$ = 1805, 1725, 1250, 1025, 810, 680 cm –1 .…”

One‐pot Modification of Terpene's Methylenecyclobutane Derivatives

“…As the first investigation object, we chose the methylenecyclobutane derivative of d (+)‐camphor prepared by a reported procedure .…”

“…Methylenecyclobutane derivative of terpenes ( 1 , 9 , 17 , and 24 ) prepared by a reported procedure .…”

Steroids: reactions and partial syntheses

“…52 The methylenation of 1 -methylene steroids (53) formeds3 part of a route to C( 1)-C( 1 1)-bridged steroids. Thus, exposure of the dibromoketal(54) to methyllithium afforded the insertion product (56) which underwent ring-opening to form (55). A high-yielding synthesis of spirocyclopropane-1 '2'-steroids involved54 the Simmons-Smith methylenation of 2-methylene steroids.…”