Table 1. Epimerization analysis by chiral GC/MS.

Entry	Compound	Description	Content of d-Le a
1	Depsi-4	From reaction mixture b	5.6%
2	Amide-4		13%
3	Amide-4	After rearrangement of isolated depsi-4 c	4.7 e %
4	Amide-4	After rearrangement of crude reaction mixture c	8.1%
5	Amide-4	From reaction in 1 : 1 (CH3)3COH/H2O d	18%

^aIsolated peptides were hydrolyzed in 6 N DCl in D₂O, converted into volatile derivatives and analyzed by chiral GC/MS.

^b2 : 1 CH₃CN/0.05 M oxalic acid in H₂O, 50 °C, 15 h.

^c2 : 1 CH₃CN/0.05 M oxalic acid in H₂O, 1.6 M NH₃, 23 °C, 3 h.

^d1 : 1 (CH₃)₃COH/H₂O, 0.1 M oxalic acid, 60 °C, 15 h.

^eThe slightly lower content of d-Leu after rearrangement is probably a result of the isolation by preparative HPLC.