New diastereomerically pure aminodiol ligands from (R)-(-)-phenylglycinol and cyclohexene oxide. Synthesis and characterization of the ligands and of their dioxomolybdenyl complexes

The reaction of (R)-phenylglycinol with cyclohexene oxide at 100 degrees C gives a 1:1 mixture of the beta-aminodiols [HOCH2-(R)-PhCH]NH[(R)-cyclohexan-(R)-2-ol][(R)-(R)-(R)-HNCyOH(2)] and [HOCH2-(R)-PhCH]NH[(S)-cyclohexan-(S)-2-ol][(R)-(S)-(S)-HNCyOH(2)]. Recrystallization of the crude reaction product from hot toluene gave the (R)-(R)-(R) diastereomer in 33% yield. By addition of petroleum ether to the filtrate, diastereomerically pure (R)-(S)-(S)-HNCyOH(2) was obtained in 12% yield. The aminodiol (R)-(R)-(R)-HNCyOH(2) has been methylated at nitrogen to give [HOCH2-(R)-PhCH]NCH3[(R)-cyclohexan-(R)-2-ol][(R)-(R)-(R)-MNCyOH(2)]. The absolute configuration of all stereocenters in the latter aminodiol has been determined by an X-ray diffraction analysis. H-1 NOESY spectroscopy has been used to determine the relative configuration at each stereocenter in the dioxomolybdenyl complexes (R)-(R)-(R)-(R)-(HNCyO)MoO2 (1) and (R)-(R)-(R)-(R)-(MNCyO)MoO2 (2) in which a fourth asymmetric center is originated by the stereoselective coordination of the nitrogen donor atom.