Regioselectivity in the Hydroboration of Steroidal Δ³-Allylic Alcohols†

Abstract

The presence of an allylic 5α-hydroxy group in an androst-3-ene increases the proportion of addition of a borane to the adjacent C-4 compared to the unsubstituted steroid and directs the addition to the face of the alkene anti to the hydroxy group with stereochemical effects that may oppose those of the C-10β-methyl group.

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