Figure 1.

Synthesis of N-{2-[3-(17-Acetyl-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yloxycarbonyl)propionylamino]-ethyl}-succinamic acid 10,13-dimethyl-3-oxo-hexadecahydro-cyclopenta[a]phenanthren-17-yl-ester (3). Reaction of N-(2-amino-ethyl)-succinamic acid 17-acetyl-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[á]phenanthren-3-yl-ester (1) and hemisuccinate dihydrotestosterone (2) using boric acid as catalyst (i).