The meso‐2,3‐diphenylpiperazine was prepared in 86 % yield with 99:1 dr from the readily accessible 5,6‐diphenyl‐2,3‐dihydropyrazine by NaBH4/MeOH reduction. The corresponding diastereomeric amides prepared using (R)‐(‐)‐menthyl chloroformate, after separation, benzylation and hydrolysis gave both isomers of optically active N‐benzyl‐2,3‐diphenylpiperazine samples in up to 94 % ee which after further enrichment using the simple achiral oxalic acid afforded samples of both enatiomers in 99 % ee. Reaction of the chiral optically active N‐benzyl‐2,3‐diphenylpiperazine with terminal alkynes and aldehydes in the presence of ZnCl2 gave the corresponding propargylamines with very high diasterioselectivities (up to 99:1 dr) from which both enantiomers of chiral allenes were obtained in up to 82–86 % ee by reaction with ZnBr2 in toluene at 120 °C.

A simple one‐pot transformation of secondary alcohols to α‐hydroxy ketones using pyridinium dichromate (PDC) in DMF has been developed and substrate scope tested with 25 compounds of hydantoin derivatives. Using this method, we have devised a common dihydroxy intermediate and synthesized four natural products oxoaplysinopsins D, E, F, and G for the first time.