Aplysinopsin-type alkaloids from Dendrophyllia sp., a scleractinian coral of the family dendrophylliidae of the philippines,facile photochemical (Z/E) photoisomerization and thermal reversal

The dendrophylliid Dendrophyllia sp. of Palawan contains the indole alkaloids 2′-demethylaplysinopsin ( 4 ) and 2′-demethyl-3′-N-methylaplysinopsin ( 6 ) and their 6-bromo analogues in H (Z/E) ratio larger than 95:5; these mixtures undergo facile photoisomerization to give mixtures richer in the (E) stereoisomer which undergo thermal isomerization to give back the original mixtures.