| 摘要 |
<p>A process for preparing a compound of formula (I) <CHEM> (in which R<1> represents methyl, ethyl or isopropyl group, R<2> represents a hydrogen atom or a methyl or acetyl group and R<3> represents a hydrogen atom, or OR<2> and R<3> together with the carbon atom to which they are attached represent the group >C=0) which comprises oxidising a corresponding 23 alpha -OH compound in the presence of a phase transfer catalyst.</p> |
