Homochiral 4-hydroxy-5-hexenoic acids and their derivatives and homologues from carbohydrates
摘要:
Efficient routes to chiral 4-hydroxy-5-hexenoic acids and lactones from D-gluconic acid-delta -lactone and L-mannonic acid-gamma -lactone are described. In this approach, the starting lactones are converted to 2,6-dibromo compounds that readily undergo zinc mediated elimination to generate the terminal alkene group in concert with 2-deoxygenation. The integrity of the remaining stereocenters is preserved during the reaction. The related important pharmaceutical intermediates (S)-3-hydroxy-4-pentenoic acid and (S)-1.3-dihydroxy-4-pentene were also prepared from 2-deoxyribose via the corresponding aldonolactone. (C) 2001 Elsevier Science Ltd. All rights reserved.
Homochiral 4-hydroxy-5-hexenoic acids and their derivatives and homologues from carbohydrates
摘要:
Efficient routes to chiral 4-hydroxy-5-hexenoic acids and lactones from D-gluconic acid-delta -lactone and L-mannonic acid-gamma -lactone are described. In this approach, the starting lactones are converted to 2,6-dibromo compounds that readily undergo zinc mediated elimination to generate the terminal alkene group in concert with 2-deoxygenation. The integrity of the remaining stereocenters is preserved during the reaction. The related important pharmaceutical intermediates (S)-3-hydroxy-4-pentenoic acid and (S)-1.3-dihydroxy-4-pentene were also prepared from 2-deoxyribose via the corresponding aldonolactone. (C) 2001 Elsevier Science Ltd. All rights reserved.
derivatives, in which the macrocycle of natural largazole is extended by one methylene group, were prepared by the recently developed rhodium‐catalyzed hydrocarboxylation reaction onto allenes. This strategy gives access to both the (18S)‐ and (18R)‐stereoisomers in high stereoselectivity under ligand control.
allylic alcohols of ω‐alkenoic acids and derivatives thereof are highly important building blocks for the synthesis of biologically active compounds. The direct enantioselective CH oxidation of linear terminal olefins offers the shortest route toward these compounds, but known synthetic methods are limited and suffer from low selectivities. Described herein is an enzymatic approach using the P450
Asymmetricallylic alkylation (AAA) is a powerful method for the formation of highly useful, non-racemic allylic compounds. Here we present a complementary enantioselective process that generates allylic lactones via π-acid catalysis. More specifically, a catalytic enantioselective dehydrative lactonization of allylicalcohols using a novel PdII-catalyst containing the imidazole-based P,N-ligand (S)-StackPhos
and low E factor. This success can be ascribed to the higher reactivity of allylic alcohols as compared with the allyl ester products in soft Ru/hard Brønstead acid combined catalysis, which can function under slightly acidic conditions unlike the traditional Pd-catalyzed system. Detailed analysis of the stereochemical outcome of the reaction using an enantiomerically enriched D-labeled substrate
LIGAND FOR ASYMMETRIC SYNTHESIS CATALYST, AND PROCESS FOR PRODUCTION OF ALPHA-ALKENYL CYCLIC COMPOUND USING SAME
申请人:Kitamura Masato
公开号:US20120220780A1
公开(公告)日:2012-08-30
Disclosed are: a ligand for an asymmetric synthesis catalyst; and a process for producing an α-alkenyl cyclic compound using the ligand. Specifically disclosed are: a ligand for an asymmetric synthesis catalyst, which is represented by any one of formulae (1) to (4) [wherein R
1
represents —Cl or —Br; R
2
represents —CH
3
or —CF
3
; and R
3
represents —CH
2
—CH═CH
2
or —H]; and a process for producing an α-alkenyl cyclic compound using the ligand.