Figure 1. chiral starting materials. We chose r-cysteine and Dp-hydroxyphenylglycine. The construction of the crucial 6-lactam ring requires the bond-forming reactions shown in Figure I. The bond formation between the a-amino group of Dphydroxyphenylglycine and the carboxyl of L-cysteine was a relatively trivial amide group synthesis. However, the second bond formation, that of the amino group to C-4 while retaining the chirality at C-3, ...
