The identity of eriocarpin with desglucosyrioside (1 ) has been established by comparison of their triacetates. 13C and 'H N.m.r. spectra show that the conversion of labriformidin into desglucosyrioside involves solely the reduction of a 3-keto-function in the carbohydrate portion (B) which is identical (in structure and stereochemistry) with that in uscharidin (7). Structures are proposed for labriformidin and labriformin. 13C N.m.r. data establish the @-configuration of the 7.8-epoxide in labriformidin, desglucosyrioside, and in the 5P-cardenolide sarverogenin (1 1 ).RECENTLY the toxic cardenolide glycosides, labri-cardenolides of the Asclepiadaceae has been described formidin, labriformin, and eriocarpin were isolated from in the preceding paper.4 AscZepias eriocarpa of the milkweed family (Asclepi-A feature of the 4,6-dideoxyhexosulose moiety ( A ) of adaceae), and shown t o be present also in A . Zabviformis the Asclepiadaceae cardenolides is that the tertiary 2'and A . erosa.l I n this paper we propose structures (2) hydroxy-group may be a~e t y l a t e d .~-~ While eriocarpin Labriformidin on sodium borohydride reduction gave desglucosyrioside (1) as one of the pr0ducts.l Comparison of the 13C n.m.r. spectra' shows that the Also shown by t.1.c. (see Experimental Section). process involves reduction of o w ketone function to a