Citation: S. Noguchi et al., REACTION OF STEROID-17-ALPHA-HYDROXY-17-CARBOXYLIC ACIDS WITH CARBODIIMIDES - SYNTHESIS OF STEROID-17-SPIRO-5'-[2'-IMINO-4'-OXAZOLIDINONES]AND 17-SPIRO-5'-[2',4'-OXAZOLIDINEDIONES], Chemical and Pharmaceutical Bulletin, 42(8), 1994, pp. 1567-1570