advantages conferred by the phosphetane ligands are evident although the reason for such a significant increase in selectivity upon moving from a five membered ring to a four membered phosphorus heterocycle is unclear table 3 reports the result obtained from asymmetric hydrogenation of u201c inverse u201d itaconate 5 the term u201c inverse u201d refers to the protection pattern of the itaconate and implies an inverse of ester acid protection relative to standard stobbe derived itaconates it can be seen that the rhodium complexes of duphos dipamp and bppm ligands were inadequate with regard to both catalytic efficiency and enantioselectivity entries 1 4 in order to test this further the rhodium catalyst of the phanephos ligand did render acceptable rates although ee 39 s were low entry 5 likewise catalysts bearing the fc 5 me amd fc 5 et ligands were highly active yet performed poorly in terms of enantioselectivity entries 9 10 catalysts based on the novel ligands especially fc 4 et and fc 4 pr were very efficient in this process entries 6 8 table 4 shows results from hydrogenation of the u03b2 substituted inverse itaconate ester 6 rhodium complexes of fc 4 et and fc 4 pr ligands were found to promote highly enantioselective hydrogenation with good substrate conversion entries 1 2 in contrast the bppm catalyst was completely ineffective entry 3 this process was investigated since amidosuccinate derivatives of type 8 have served as versatile peptidomimetic intermediates for the construction of various important drug candidates the substrates represented by formula 7 are another class of u201c inversely u201d protected itaconates results are shown in tables 5 7 for the specific substrates 9 and 10 tables 5 and 6 compare the performance of the rhodiun complex of fc 4 et with rhodium complexes of a broad range of.