[Studies in the synthesis of the series of 3.6-epidithio-2,5-dioxo-piperazine antibiotics gliotoxin, sporidesmin, aranotin, chaetocin, and verticillin. V. Preparation of epitrithio- and epitetrathio-L-prolyl-L-proline anhydride]

[Studies in the synthesis of the series of 3.6-epidithio-2,5-dioxo-piperazine antibiotics gliotoxin, sporidesmin, aranotin, chaetocin, and verticillin. V. Preparation of epitrithio- and epitetrathio-L-prolyl-L-proline anhydride]