Diphosphinite ligands 2 and 3, easily prepared from inexpensive D(+)-xylose in few steps, were tested in the Rh-catalyzed asymmetric hydroformylation of several vinyl arenes. High regio-selectivities in branched aldehyde (up to 99%) and moderate enantio-selectivity (up to 63%) were found (20-40 degrees C, 30-60 bar of syn gas). For the first time, the structure in solution of the species formed under hydroformylation conditions with diphosphinite ligands was determined. (c) 2004 Elsevier B.V. All rights reserved.