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■ Absolute Stereo-structure of Kendarimide A, a Novel MDR Modulator, from a Marine Sponge

Naoyuki Kotoku, Liwei Cao, Shunji Aoki, and Motomasa Kobayashi*

*Graduate School of Pharmaceutical Sciences, Osaka University, Yamadaoka 1-6, Suita, Osaka 565-0871, Japan

Abstract

The absolute stereostructure of two N-methylcysteines in kendarimide A (1), a novel linear peptide reversing multidrug resistance (MDR) mediated by P-glycoprotein, was determined by comparison with synthetic model compounds. For this purpose, four diastereomers (17a-d) of the C-terminal tetrapeptides in kendarimide A (1), containing L,L-, L,D-, D,L-, D,D-N-methylcysteinyl-N-methylcysteine, were synthesized. The absolute configuration of both the two adjacent N-methylcysteines in 1, which form an eight-membered disulfide ring (ox-[MeCys-MeCys]), was elucidated to be L-configuration by comparison of the NMR spectral data of the four model tetrapeptides with that of kendarimide A (1).