New malyngamides from the Hawaiian cyanobacterium Lyngbya majuscula

Isomalyngamides A and B (1, 2) were isolated and characterized from a colle ction of the cyanobacterium Lyngbya majuscula from Hawaiian waters. These c ompounds represent a new type of malyngamide, similar to malyngamides Q and R, in which the conformation of the chloromethylene group is opposite from the majority of previously reported malyngamides. The geometry of the chlo romethylene moiety was elucidated from the long-range coupling constants (( 3)J(C-H)) Obtained from editing-HETLOC and phase-sensitive HMBC experiments . Isomalyngamides A and B (1, 2) showed lethal toxicity to crayfish.