Abstract: Two novel chiral diphosphines, 1,6-bis(diphenyl-phosphino)-2,3,4,5-dibenzylidene-D-mannitol and 1,6-bis-(diphenylphosphino)-3,4-benzylidene-2,5-methylene-D-mannitolhave been synthesized from D-mannitol.The Rh(I) complexes of both chiral ligands have been used as catalysts in the asy-mmetic hydrogenation of α-acetamidocinnamic acid, but no enantioselectivity was observedin both cases, furthermore, no hydrogenation activity was Shown in the reaction in thepresence of the former ligand.A preliminary explanation of the results observed in asymmetrie hydrogenation issuggested in the paper.

Key words: D-mannitol, Chiral diphosphine, Asymmetric hydrogonation