Further study on the transformation of β-(1-hydroxybut-3-enyl)indoles into 1-β-(indolyl)buta-1,3-diene, yuehchukene, murrapanine and analogues

Abstract

β-(1-Hydroxybut-3-enyl)indoles have been converted into three indole natural products: yuehchukene 1, β-(dehydroprenyl)indole 2, murrapanine 3 and other analogues in a one step procedure under various acid-catalysed reaction conditions in THF. A one-pot synthesis of bisnoryuehchukene 15 starting from indole-3-carboxaldehyde was also achieved using a similar approach. β-(1-Hydroxybut-3-enyl)indoles are presumed to be dehydrated to 1-(β-indolyl)buta-1,3-dienes which then react further to give yuehchukene, murrapanine and other derivatives via a Diels–Alder pathway. The yields of 3 and normurrapanine 31 could be improved by using an aerial oxidation method. Murrapanine and analogues were found to exhibit potent cytotoxicity towards various cancer cell lines.