Aromatizing polymerization of 1,2-diisocyanobenzene derivatives was mediated by optically active organopalladium(II) complexes bearing 1,1′-binaphth-2-yl groups to give optically active poly(quinoxaline-2,3-diyl)s with varying screw-sense selectivities, which crucially depended upon the substituents on the binaphthyl groups. The most effective catalyst, which has 7′-methoxy-1,1′-binaphthyl group, induced the formation of a single screw-sense. Isolation and structural analyses (single-crystal X-ray diffraction and 1 H NMR spectroscopy) of intermediary [oligo(quinoxalinyl)]palladium complexes revealed that the screw-sense selection in the polymerization may be decisively governed by the diastereomeric ratios of the (terquinoxalinyl)-palladium(II) complex intermediate.
Although our findings show that the open C-loop AC IOL (Simcoe) is contraindicated, implantation of the 4-point fixation AC IOL may be acceptable in selected cases.
A short and enantioselective de novo synthesis of an L-glycero-D-manno-heptose building block for the total synthesis of a Yersinia pestis cell wall polysaccharide is described.
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