Substantially less toxic metal impurity than when unbound chiral complexes are used—this is achieved by the first polymer‐supported chiral catalysts for olefin metathesis. These allow for efficient synthesis of various unsaturated carbo‐ and heterocycles in high optical purity through ring‐opening (see scheme) and ring‐closing reactions.
Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are recommended components of preferred combination antiretroviral therapies used for the treatment of HIV. These regimens are extremely effective in suppressing virus replication. Structure-based optimization of diaryl ether inhibitors led to the discovery of a new series of pyrazolo[3,4-c]pyridazine NNRTIs that bind the reverse transcriptase enzyme of human immunodeficiency virus-1 (HIV-RT) in an expanded volume relative to most other inhibitors in this class.The binding mode maintains the beta13 and beta14 strands bearing Pro236 in a position similar to that in the unliganded reverse transcriptase structure, and the distribution of interactions creates the opportunity for substantial resilience to single point mutations. Several pyrazolopyridazine NNRTIs were found to be highly effective against wild-type and NNRTI-resistant viral strains in cell culture.
An enantiomerically pure Mo-based complex that bears an alkylimido ligand is prepared and characterized through NMR spectroscopy and X-ray analysis. Mo complex 4 is the only reported chiral alkylimido catalyst; all previous chiral complexes are arylimido systems. These studies show that the chiral Mo catalyst exists exclusively as the syn isomer and that it offers unique reactivity and selectivity profiles in asymmetric olefin metathesis.
The Mo-catalyzed asymmetric ring-closing metathesis (ARCM) of various achiral trienes leads to the formation of medium-ring unsaturated heterocycles in high yield and with excellent enantioselectivity. Reactions may be carried out on gram scale and in the absence of solvent. The unsaturated siloxanes obtained enantioselectively can be readily functionalized to obtain synthetically useful and difficult-to-access tertiary alcohols.
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