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.