Synthesis of 1-Aza-cryptophycin 1, an Unstable Cryptophycin. An Unusual Skeletal Rearrangement

A total synthesis of cryptophycin 337 (1-aza-cryptophycin 1, 2), an analogue of the potent antitumor antibiotic cryptophycin 1 (1), is described. Cryptophycin 337 was unstable and underwent an unexpected skeletal rearrangement. (R)-Mandelic acid was used as the sole source of asymmetry for the synthesis of unit A.