Chiroptical properties and enantioselectivity in hydrogenation with rhodium(I) complexes of chiral bis-diphenylphosphines derived from -glucose and -galactose

(2R,3S)-2-Diphenylphosphinomethyl-3-diphenylphosphinotetrahydropyran (3) has been prepared in 64% yield from the dimesylate 5, derived from -galactose. The surprisingly different reactivities of dimesylates 2 and 5 towards diphenylphosphide anion are considered and the conformational properties of 1–6 discussed in terms of their CD spectra. The rhodium(I) complexes 9 and 10 exhibit low to relatively high enantioselectivities in hydrogenation of Z-α-acetylaminocinnamic acid and α-acetylaminoacrylic acid. The chiroptical and conformational properties of the bidentate ligands (3, 6), and their rhodium(I) complexes (9, 10) are correlated with the observed enantioselectivities.