In a better procedure than the known for (rac)-2a, the diamine (rac)-2b was resolved for the first time with the new resolving agent (R, R)-and (S, S)-2, 3-di (phenylamino-carbonyl) tartaric acid (5c)(40–45% weight yields;> 99% ee). The diamines (R)-or (S)-2a and 2b were converted with> 98% stereochemical retention into the diiodides (R)-and (S)-3a and 3b and subsequently, without loss of optical purity, diphenylphosphinated to the known ...