A-homo-B-norsteroids

An alternative to fluorohydrin formation is observed with the 6/ -methyl-5a,6a-epoxide (30), which rearranges, possibly in a concerted reaction, to the A-homo-B-norsteroid (31) (cf, chapter 14, Vol. II). 

In the course of synthetic efforts aimed at obtaining 6j5-fluoro steroids, Kirk and Petrow treated a 3)5-acetoxy-6-raethyl-5a,6a-epoxide with boron trifluoride etherate and unexpectedly obtained a fluorine-free acetoxy ketone." Later transformations established that the product was the A-homo-B-norsteroid (104). 

High yields of A-homo-B-norsteroids are also obtained on rearrangement of the 5a,6a-epoxides from 3)3-hydroxy-6-methylandrost-5-en-17-one and Sp, 17)5-diacetoxy-6-methylandrost-5-ene. 

A-homo-B-nor-5/3-choIestan-4a-one, 394 A-homo-B-norsteroids, 389 B-homo-19-norsteroids, 379 B-homo-5a-pregnane-3, 20/3-diol diacetate, 376... 

V. 10(5 -> 6pH)Abeostero ds (A-Homo-B-Norsteroids) / 389 Solvolysis of 5a,6a-epoxy-6-methyl steroids / 389 Pinacol rearrangement of 5a-hydroxy-6a-tosylates / 392 Summary / 394... 

A promising general method for preparing B-homo-19-norsteroids has been reported by Tadanier and Cole in a study of the horaallylic rearrangements of 19-substituted-A -steroids. The ready availability of 19-hydroxy-A -steroids cf. ehapter 12) makes this approach particularly attractive. 

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