| 摘要 |
<p>method of cyclisation of substrates of the formula: (VI) wherein: (a) R1 is H or alkyl of one to four carbons; (b) R2 is H or alkyl of one to four carbons, with the proviso that R1 is H when R2 is alkyl; and with the proviso that R2 is H when R1 is alkyl; (c) R3 is a leaving group slected from the group consisting of OH, alkoxy of one to four carbons, alkoxyalkoxy of from two to about four carbons, acyloxy or from about one to about seven carbons, and trialkylsilyloxy; (d) R4 is halogen, alkoxy of from one to four carbons, hydrocarbyl of from one to about four carbons, hydrocarbyl of from one to about four carbons substituted by one or more (1) halogens or (2) alkoxy moieties of from one to two carbons; and (e) R5 is H, alkyl of one to six carbons; hydroxy, or an esterified or etherified moiety of (1) less than eight carbons selected from the group consisting of alkoxy, trialkylsilyloxy, aralkyloxy, cyclo-alkoxy, and heterocyclo-oxy radicals; (2) .alpha.-alkoxyalkoxy of from two to four carbons, and (3) acyloxy of from one to seven carbons; by way of a cyclisation step to form 6 .alpha.-substituted steroidal derivatives of the formula: and (VII) (VIII) wherein R4 and R5 have the meaning above and R6 is alkyl of from one to about four carbons. The compounds of the formulae VII and VIII are important intermediates for preparing well known biologically active 6 .alpha.-substituted steroids.</p> |
