Tantazole B is a newly isolated tolytoxin. FR900482 is a recently isolated potent antitumor antibiotic. They both have novel structural features which present challenges to the synthetic chemists. The first total synthesis and structure revision of (−)-tantazole B is described herein. A convergent methodology is developed and could be applied to the synthesis of the other members of oxazole/thiazoline family.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The first and, to date, only total synthesis of (±)-FR900482 is also described here. The stereocontrolled total synthesis of FR900482 features a facile construction of the 8-membered intermediate through reductive amination, stereospecific hydroxymethyla-tion and efficient oxidation of the amine to the hydroxylamine.