| 摘要 |
<p>A process for preparing a compound having a formula (4) or (5), in either optically-enriched or racemic form, wherein R?1, R2, R3 and R4¿ are independently selected from hydrogen, alkyl, aryl, alkaryl, aralkyl and acyl groups, comprises mixing with a plant extract an oxidative cyclisation precursor of the said compound.</p> |
