The ascidian Lissoclinum japonicum from Palau contained the antimicrobial and antifungal metabolites N,N-dimethyl-5-(methylthio)varacin (6) and 3,4-dimethoxy-6-(2'-N,Ndimethylaminoethyl)-5-(methylthio)benzotrithiane (7), both of which were isolated as the trifluoroacetate salts. An inseparable 2:3 mixture of 5-(methylthio)varacin (8) and the corresponding trithiane 9 was isolated from a different Lissoclinum species from Pohnpei and 3,4-desmethylvaracin (10), isolated as the trifluoroacetate salt, was obtained from a species of Eudistoma from Pohnpei. The pentathiepins and trithianes selectively inhibit protein kinase C.