Synthesis, Characterization, and Applicability of Neutral Polyhydroxy Phospholane Derivatives and Their Rhodium(I) Complexes for Reactions in Organic and Aqueous Media
摘要:
Two different protocols for the preparation of water-soluble, enantiomerically pure polyhydroxybisphospholanes from acid-labile acetal and tert-butyldimethylsilyl-protected derivatives are reported. These procedures circumvent two of the commonly encountered limitations in the synthesis of these potentially important ligands: (a) formation of phosphonium salts from the highly basic phosphine under acidic conditions, and (b) the need to start with preformed, fully protected cationic metal complex. Thus, cationic Rh complexes of these ligands have been prepared in a separate step, and they have been found to be excellent catalysts for organic and aqueous phase hydrogenation of dehydroamino acids. The viability of catalyst recovery has been demonstrated in three different systems, including two cases where > 99% ee can be achieved under recycling conditions.
Enantiodivergent total synthesis of naturally occurring trans-2-butyl-5-pentylpyrrolidine
作者:Nobuo Machinaga、Chihim Kibayashi
DOI:10.1016/s0040-4039(00)94464-2
日期:1990.1
The enantiodivergent totalsynthesis of (+)-(2S,5S)- and (−)-(2R,SR)-trans-2-butyl-5-pentylpyrrolidines was effected from the C2 symmetric (S,S)- and (R,R)-diepoxides, respectively, both prepared from Dmannitol, by a sequence involving stereo-defined ring construction of the unsymmetrical trans-2,5-dialkylpyrrolidine via the cyclic sulfate as a key step.
Enantioselective total synthesis of (+)- and (-)-pyrrolidine 197B, a new class of alkaloid from the dendrobatid poison frog: assignment of the absolute configuration
作者:Nobuo Machinaga、Chihiro Kibayashi
DOI:10.1021/jo00004a011
日期:1991.2
Enantioselective total synthesis of both enantiomers of pyrrolidine 197B (1), a new class of dendrobatid alkaloid, is described. The synthesis begins with the C2 symmetric S,S or R,R diepoxides 4, derived from (S,S)-1,2,5,6-hexanetetraol (2) as a single common chiral synthon, and involves pyrrolidine formation via the cyclic sulfonates to afford (+)- or (-)-1, respectively. The (+) and (-) enantiomers of 1 were converted to the corresponding N-benzoyl derivatives (+)-27 and (-)-27, which were directly compared with 27 derived from natural 1 by HPLC using a Chiralcel column. This comparison established the absolute stereochemistry of the natural enantiomer of pyrrolidine 197B as 2S,5S [(+)-1].