| 摘要 |
<p>The subject invention pertains to a process for preparing a compound having a formula (4) or (5), in either optically-enriched or racemic form, wherein R1, R2, R3 and R4 are independently selected from hydrogen, alkyl, aryl, alkaryl, aralkyl and acyl groups. In one embodiment, the process of the invention comprises mixing with a plant extract obtained from crushed daffodil bulbs or crushed snowdrop bulbs an oxidative cyclisation precursor of the compound.</p> |
