| 摘要 |
<p>The prepn. of steroids of formula (I), comprises reacting a steroid of formula (II) with an acetal of formula R3C(OR2)2 (III) in the presence of phosphorus pentoxide. In the formulae dotted line is a single or double bond; X is H, F or Me; Y and Z are each H or together form a C-C bond, or Y is H, F, Cl or Br and Z is OH; R1 is lower alkyl; R2 is H or lower acyl; R3 is lower alkyl. Corticoids (Ia) of formula (I), where X and Y are H and Z is OH are new. (I) are pharmaceuticals. Previous processes were costly and gave only low yields. The process gives high yields.</p> |
