Synthesis of the Proposed Structure of Feigrisolide C
摘要:
Possible structures of feigrisolide C were synthesized via ring-closing olefin metathesis reaction of a diester derivative prepared from 8-epinonactic acid, but physical characteristics of the synthetic samples did not match with those of the natural sample of feigrisolide C.
Enzymatic Reductions for the Regio- and Stereoselective Synthesis of Hydroxy-keto Esters and Dihydroxy Esters
摘要:
Ketoreductases were utilized for the stereoselective synthesis of delta-hydroxy-beta-keto esters, beta-hydroxy-delta-keto esters, and beta,delta-dihydroxy esters. Seven out of eight possible stereoisomers were obtained from the enzymatic reduction of the corresponding beta,delta-diketo ester in high enantio- and diastereomeric excess.
The Zn-promoted direct reduction of various ketones, including alkyl aryl ketones, α- and β-keto esters, α- and β-keto amides, into the corresponding alcohols with polymethylhydrosiloxane (PMHS) in protic conditions is reported. The reaction proceeds chemoselectively under smooth conditions, with simple catalyst combinations based on a zinc precursor [ZnEt2, Zn(OMe)2, Zn(OH)2] and a 1,2-diamine ligand
A convergent synthetic route to the fungal metabolites cladosins B and C has been developed, affording these natural products in 29% and 27% overall yield, respectively. The cladosins are rare examples of hybrid polyketides featuring a 3-enamine tetramic acid group derived from l-valine. Key steps in this modular six-step sequence include a DMAP-mediated O- to C-acyl rearrangement to unite the side
Asymmetric hydrogenation of methyl 3,5-dioxohexanoate catalyzed by ru-binap complex: a short step asymmetric synthesis of dihydro-60methyl-2-H-pyran-2-one
Hydrogenation of methyl 3,5-dioxohexanoate 3 using Ru2Cl4((R) or (S)-binap)2(NEt3) as the catalyst gave dominantly anti 3,5-dihydroxyester 9, which was then converted into unsaturated lactone 4. The pathway of the hydrogenation reaction was also investigated.
Diastereoselective synthesis of syn-3,5-dihydroxyesters via ruthenium-catalyzed asymmetric transfer hydrogenation
The asymmetric transfer hydrogenation of chiral 5-hydroxy-3-ketoesters in 2-propanol using chlororuthenium(II)arene/ P-amino alcohol in situ catalyst combinations or a pre-synthesized Ru-beta-amino alcohol} true catalyst, provides syn-3,5-dihydroxyesters in high yields and up to 80% de. (C) (2)002 Elsevier Science Ltd. All rights reserved.