Studies on Wittig rearrangement of furfuryl ethers in steroidal side chain synthesis

Wittig rearrangement of 17(20)-ethylidene-16-furfuryloxy steroids was examined. Reaction of 17E(20)-ethylidene-16α-furfuryloxy steroid with t-BuLi in THF afforded (20S,22S)- and (20S,22R)-22-hydroxy steroids , and 17Z(20)-ethylidene-16α-(2-furyl)hydroxymethyl steroid in 61, 28, and 9% yields, respectively. Base treatment of 17E(20)-ethylidene-16β-furfuryloxy steroid gave (20R,22R)-22-hydroxy steroid and 17Z(20)-ethylidene-16β-(2-furyl) hydroxymethyl steroid in 60 and 17% yields. In contrast, 17Z(20)-ethylidene-16-furfuryloxy steroids , led to the corresponding 2,3-rearranged products in low yields (25% for (20R,22S)-22-hydroxy steroid ; 31% for (20S,22R)-22-hydroxy steroid ). Both (20S,22S)- and (20S,22R)-22-hydroxy steroids , were converted by catalytic hydrogenation into known compounds , , key intermediates for the synthesis of biologically active steroids.