Syntheses and interfacial behaviour of neoglycolipid analogues of glycosyl ceramides
摘要:
Four glycosyl ceramides analogues having D-galactose or 2-acetamido-2-deoxy-D-glucose moieties linked to enantiomeric lipids have been synthesised to study their interfacial behaviour at the air \ water interface. The lipid chains were prepared in two steps by opening 1,2-epoxyhexadecane using Jacobsen kinetic hydrolytic resolution (KHR) followed by an azidosilylation reaction of the diol so obtained. Glycosylation reactions were realised either with 2,3,4,6-tetra-O-benzoyl-alpha -D-galactopyranosyl trichloroacetimidate or 1,3,4,6-tetra-O-acetyl-2-allyloxycarbonylamino-2-deoxy-beta -D-glucopyranose as donors and (2R)- or (2S)-2-azidohexadecanol derivatives as acceptors. Transformation of the azido glycosides into N-acylated products was done by a modified Staudinger reaction in the presence of fatty acyl chlorides. The four neoglycolipids are able to form a condensed monolayer at the air \ water interface; their pi -A isotherm diagrams are similar to that described for the natural glycosyl ceramides. The detailed analysis of the isotherms, taking into account the chirality of the lipid chains, allowed to determine the contribution of the different parts of the molecule under the monolayer packing. (C) 2001 Elsevier Science Ltd. All rights reserved.
(Z)-(2′R)-1-O-(2′-methoxynonadec-10′-enyl)-sn-glycerol, a new analog of bioactive ether lipids, was synthesized from oleic acid and 2,3-isopropylidene-sn-glycerol. The two key steps of this synthesis were the conversion of oleyl aldehyde to a monounsaturated epoxideusing Matteson’s method followed by hydrolytic kinetic resolution and a nucleophilic epoxide opening by 2,3-isopropylidene-sn-glycerol in the presence
(2R)-(+)- and (2S)-(−)-2-iodohexadecanal 1 with ee's ≥ 89% were synthesized in five steps and 62% overall yield from chiral enol ethers , via the iodocyclization with IC1 and chromatographic separation of the resulting diastereomeric 1′-iododioxanes 8. The ee's of have been determined after their transformation to the (R)-O-methylmandelate esters 11 and 12 or to the epoxides , respectively. Their absolute
Aminoalcohol lipidoids are prepared by reacting an amine with an epoxide-terminated compound are described. Methods of preparing aminoalcohol lipidoids from commercially available starting materials are also provided. Aminoalcohol lipidoids may be prepared from racemic or stereochemically pure epoxides. Aminoalcohol lipidoids or salts forms thereof are preferably biodegradable and biocompatible and may be used in a variety of drug delivery systems. Given the amino moiety of these aminoalcohol lipidoid compounds, they are particularly suited for the delivery of polynucleotides. Complexes, micelles, liposomes or particles containing the inventive lipidoids and polynucleotide have been prepared. The inventive lipidoids may also be used in preparing microparticles for drug delivery. They are particularly useful in delivering labile agents given their ability to buffer the pH of their surroundings.
Stereoselective total syntheses of the antiprotozoal natural product (+)-passifloricin A and its C-6 epimer have been achieved in similar to 5% overall yield. The strategy is based on Jacobsen epoxidation, Grubbs' metathesis and an Evans' intramolecular oxa-Michael reaction. (c) 2008 Elsevier Ltd. All rights reserved.
A convenient resolution of long-chain alkyl epoxides with Jacobsen's salen(Co)III(OAc) catalysts
作者:Prashant S Savle、Marika J Lamoreaux、John F Berry‡、Richard D Gandour
DOI:10.1016/s0957-4166(98)00175-x
日期:1998.6
Non-racemic terminal long-chain alkyl epoxides are prepared from racemic epoxides and 1 mol% (R,R)- and (S,S)-salen(Co)III catalysts following a modified procedure for kinetic resolution. The ee's for all epoxides (C-10, C-12, C-14, C-16, C-18, C-20) exceed 95% and the chemical yields range from 85% to 95%. (C) 1998 Elsevier Science Ltd. All rights reserved.