Development of practical metal-catalyzed carbenoid reactions for environmentally benign chemistry

Stereoselective Synthesis of C3-C12 Dihydropyran Portion of Antitumor Laulimalide Using Copper-catalyzed Oxonium Ylide Formation-[2,3] ShiftCopper-catalyzed oxonium ylide formation-[2,3] shift of (5S,7R)-5-allyloxy-1-diazo-8-(p-methoxybenzyloxy)-7-methyl-2-octanone proceeded in tetrahydrofuran-dichloromethane (4:1) under reflux with an excellent stereoselectivity (97:3) to give (2R,6S)-2-allyl-6-[(2R)-3-(p-methoxybenzyloxy)-2-methylpropyl]-3-dihydropyranone (2) as a major isomer in 82% yield. The resultant pyranone was converted to the key intermediate of the Mulzer's laulimalide synthesis and its derivatives.Synthesis of an Immunomodulator (+)-Conagenin and Its Analogs using Dirhodium(II)-catalyzed C-H AminationStereoselective synthesis of an immunomodulator (+)-conagenin was achieved. Both amine and carboxylic acid moieties were prepared from commercially available optically active methyl 3-hydroxy-2-methylpropanoate using dirhodium(II)-catalyzed C-H amination and chelation-controlled reductions as key steps. In addition, demethyl analogs of conagenin were synthesized using similar procedures.Dirhodium(II)-catalyzed C-H Amination Reaction of (S)-3-(tert-Butyldimethylsilyloxy)-2-methylpropyl Carbamate : A Facile Preparation of Optically Active Monoprotected 2-Amino-2-methyl-1,3-propanediolDirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate, which was easily prepared from methyl (S)-2-methyl-3-hydroxypropanoate, proceeded more smoothly than those of their 2-(methoxycarbonyl)propyl derivative to give the corresponding oxazolidinone in excellent yield. The resulting oxazolidinone was converted efficiently into both (R)-monoprotected and (S)-monoprotected 2-amino-2-methyl-1,3-propanediols.Enantioselective Synthesis of Pachastrissamine (Jaspin B) using Dirhodium(II)-catalyzed C-H Amination and Asymmetric Dihydroxylation as Key StepsEnantioselective total synthesis of anhydrophytosphingosine pachastrissamine (jaspin B) was achieved using the Sharpless asymmetric dihydroxylation and dirhodium(II)-catalyzed C-H amination as key steps.