ETHYNYLATION OF 17ALPHA-HYDROXYPREGNENOLONE 3-ACETATE . STEREOCHEMISTRY AND ACID-CATALYZED REARRANGEMENT OF REACTION PRODUCT

The ethynylation of 17α-hydroxypregnenolone 3-acetate (4) in the presence of lithium amide in liquid ammonia has been found to give only one product, 5. The absolute configuration at C-20 of 5 has been determined by catalytic reduction to 2Oβ-ethylpregn-5-ene-30,17α,20α-triol (6), which has been independently synthesized by condensation of 17α-hydropregnenolone 3β-acetate with ethylmagnesium bromide. The synthesis of the 20-diastereoisomer of 6 by condensation of methylmagnesium bromide with the 21 homolog 7 of 17α-hydroxypregnenolone 3-acetate is also reported. The acetylenic glycol 5 underwent a Wagner-Meerwein rearrangement on treatment with formic acid or thionly chloride. The structure and stereochemistry of the resulting D-homo ketone 17 has been determined. The reaction of 5 with thionyl chloride in the present of pyridine, however, gave a cyclic sulfite, 15. © 1969, American Chemical Society. All rights reserved.