Antiviral and antitumor agents from a New Zealand sponge, Mycale sp. 2. Structures and solution conformations of mycalamides A and B

Mycalamide B (2) has been found to occur with mycalamide A (1) in a New Zealand sponge of the genus Mycale. Both are potent antiviral and antitumor agents. The solution conformations of mycalamide A (1) have been explored in detail by analysis of 1H-1H coupling constants and NOE interactions and modeled by molecular mechanics calculations. Significant populations of several solution conformations were indicated. A comparison of 1H NMR data showed that analogous conformations were present in solutions of mycalamide B (2) and the structurally similar compounds pederin (4) and onnamide A (6).