Glycosides from the North Atlantic sea cucumber Cucumaria frondosa V - Structures of five new minor trisulfated triterpene oligoglycosides, frondosides A7-1, A7-2, A7-3, A7-4, and isofrondoside C

Seven highly polar trisulfated triterpene glycosides belonging to the frondoside A7 group have been isolated from the North Atlantic sea cucumber Cucumaria frondosa. The structures of five new glycosides, frondosides A7-1 (1), A7-2 (2), A7-3 (3), A7-4 (4), and isofrondoside C (5) were elucidated, three of which contained lanostane aglycons without a lactone-ring. Three pairs of the glycosides proved to be isomers by virture of the positions of double bonds in the aglycons nuclei; two pairs of the glycosides differed from each other by the character of the oxygen functionality at C-22. The results from these studies provided the basis for postulating the biosynthetic pathways of norlanostane glycosides in the sea cucumber.