Highly Diastereoselective Synthesis of N-Boc Dolaisoleuine, Unusual Amino Acid in Dolastatin 10

Photolysis of 5-phenylthiooxazolidin-2-one (4) in the presence of (n-Bu 3 Sn) 2 and n-Bu 3 SnCH 2 CH=CH 2 afforded 5-allyl derivative (5) which was led to N-Boc dolaisoleuine (11), one component of dolastatine 10 (2), via 6-10