Enantioselective synthesis of gamma,delta-disubstituted beta-hydroxy delta-lactones from furans: Synthesis of (+)-prelactone B and its C-4 epimer

A new method for the enantioselective synthesis of gamma,delta-disubstituted beta-hydroxy delta-lactones (5,6-dialkyl-5,6-dihydropyran-2-ones) is reported and exemplified for (+)-prelactone B and its C-4 epimer. Our approach is based on the ring-enlargement of suitably functionalized optically pure 4-hydroxycyclopentanones, which are readily obtained from chiral 4-hydroxycyclopent-2-enones derived from furans. The procedure is amenable to the large-scale synthesis of the title compounds

Asymmetric synthesis of cyclopentenones with benzylic alpha-quaternary carbon stereogenic centres from furans

A new procedure for the synthesis of cyclopentenones containing benzylic alpha-quaternary carbon stereogenic centres is reported. This method makes use of a one-pot alkylation-elimination sequence from readily available starting materials and simple procedures, which makes it useful for the large-scale preparation of densely functionalised cyclopentanoids. (C) 2004 Elsevier Ltd. All rights reserved

Regio- and stereoselective addition of Grignard and organolithium reagents to 4-hydroxy-2-cyclopentenones

a highly regio- and stereoselective method for the 1,2- or 1,4-addition reactions to 4-hydroxy- 2-cyclopentenones has been devised, which makes use of readily available organolithium and Grignard reagents. This procedure allows for stereochemistry complementary to that observed in the 1,4-addition of organocuprates and makes possible the attachment of aromatic groups to carbons C-2 and C-3 of cyclopentenones 5 or 6 and carbons C-4 and C-5 of cyclopentanones 7, which are of interest for further elaboration into biologically active target

Regioselective synthesis of trisubstituted cyclopentadienyl ligands from furans

1,2,3- And 1,2,4-trisubstituted cyclopentadienyl manganese tricarbonyl compounds have been synthesized regioselectively from furans following a common synthetic strategy. The key steps include the transformation of furylcarbinols into hydroxycyclopentenones followed by the conjugate addition of Grignard reagents under chelation directed conditions. This affords hydroxycyclopentanones which can be dehydrated to cyclopentenones. These compounds are further elaborated into the final targets by the 1,2-addition of organolithium reagent

Asymmetric C-C bond formation by the mixed oxidative coupling of 1,1 '-bi-2-naphthyl esters

Asymmetric C-C bond formation was effected by the oxidative coupling of two different ester enolates using (R)-(+)-1,1'-bi(2-naphthol) as a common tether which served to link together both ester moieties in an asymmetric environment. Reduction of the corresponding succinates afforded diastereomerically pure 2,3-disubstituted-1,4-butanediols

Stereoselectivity control in the Rh(I)-catalyzed conjugate additions of aryl and alkenylboronic acids to unprotected hydroxycyclopentenones

The stereoselective Rh(I)-catalyzed conjugate addition reaction of aryl and alkenylboronic acids to unprotected 2-phenyl-4-hydroxycyclopentenone is presented. The free OH group on the substrate is responsible for the stereochemistry, which is cis for arylboronic derivatives. In the case of the alkenylboronic compounds, the stereochemistry can be tuned to either a cis (bases as additives) or trans addition (CsF as additive) without the need of protecting groups