Stereochemistry of theonezolides A–C

Theonezolides A–C (1–3) are cytotoxic 37-membered macrolides with a long side chain isolated from an Okinawan marine sponge Theonella sp. The relative stereochemistry of 1–3 was investigated by combination of NMR analysis including application of a JBCA method, a Universal NMR database, and a 13C-acetonide method. Furthermore, the absolute configurations at 14 chiral centers in 1–3 were found to be 19S, 22R, 24S, 28S, 44S, 45S, 47R, 49S, 53R, 55S, 57S, 59S, 60S, and 63S by application of a modified Mosher’s method.