Annunziata Soriente

An efficient asymmetric aldol reaction of Chan's diene promoted by chiral Ti(IV)–BINOL complex

Abstract 1,3-Bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene (Chans diene) can be conveniently used in asymmetric aldol reaction with aromatic, heteroaromatic, α,β-unsaturated and aliphatic aldehydes in the presence of catalytic amounts (2–8% mol) of chiral Ti(IV)/( R )-BINOL complex.

Enantioselective aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene promoted by chiral Ti(IV)/BINOL complex

Abstract Enantiomerically enriched δ-hydroxy-β-ketoesters are easily available by aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene in the presence of Ti(O-iPr)4/(S)-(−)-BINOL system. All reaction mixtures were separated by column chromatography and mostly isolated in moderate to good yields and all in high enantiomeric excesses.

Enantioselective aldol condensation of O-silyl dienolates to aldehydes mediated by chiral BINOL–titanium complexes

Abstract Chiral BINOL–titanium complexes have been shown to catalyze enantioselective aldol reactions between dioxinone derivatives and a set of aldehydes. The aldol adducts are isolated in good yields and high enantioselectivities. A range of substitution patterns on the O-silyl dienolate is possible: alkyl and benzyl substituents are tolerated. A simple reaction protocol is described and provides an efficient alternative to the well-known methods for conducting enantioselective Mukaiyama aldol reactions.

SOLVENT FREE REACTION UNDER MICROWAVE IRRADIATION : A NEW PROCEDURE FOR EU+3 : CATALYZED MICHAEL ADDITION OF 1,3-DICARBONYL COMPOUNDS

CC bond formation via Michael addition is achieved in high yields and short times by employing catalytic amounts of EuCl3 in dry media under microwave irradiation.

Heterocyst glycolipids of the cyanobacterium Cyanospira rippkae

Abstract The heterocyst glycolipids of the cyanobacterium Cyanospira rippkae have been isolated and their structures established to be 1-(O-α- d -glucopyranosyl)-3R,27R-octacosanediol and 1-(O-α- d -glucopyranosyl)-27-keto-3R-octacosanol by spectroscopic and chemical means. The absolute configuration at the two stereogenic centres in the aglycone moiety of the former compound has been established in a single step by Moshers method on the triol derivative. The akinetes of C. rippkae contain the same glycolipids.

A convenient catalytic procedure for the highly enantioselective aldol condensation of O-silyldienolates

Abstract In the presence of catalytic amount of chiral Ti(OiPr)4/BINOL (0.08 equiv.) the asymmetric aldol condensation of 6-methyl-4H-[1,3]-dioxin-4-one-derived silyloxydienes takes place in high yields and enantiomeric excesses with aromatic, heteroaromatic, unsaturated and aliphatic aldehydes. Notable amplification of enantiomeric excesses have been obtained by using enantioenriched catalytic systems.

Kinetic resolution and asymmetric oxidation as combined routes to chiral sulfoxides

Abstract Non-racemic sulfoxides are accessible through a modified Sharpless kinetic resolution of racemic sulfoxides. Furthermore, thanks to enantioconvergence of asymmetric oxidation and kinetic resolution a successful improvement of e.e. is achievable.

First enantioselective synthesis of manoalide: application of aldehyde–dioxinone enantioselective condensation

Abstract Manoalide, an analgesic and anti-inflammatory sesterterpene, has been stereoselectively synthesized for the first time. The C-4 stereogenic centre has been introduced in an early step by enantioselective aldol condensation using a Ti(OiPr)4/(R)-(+)-binol complex.

Structure of the “heterocyst glycolipids” of the marine cyanobacterium Nodularia harveyana

Abstract The “heterocyst glycolipids” have been reported to take part in the protection of the specialized cyanobacterial cells capable of N2 fixation against the penetration of O2. For the first time such glycolipids have been isolated in a pure form from a cyanobacterium, Nodularia harveyana , and their structures have been established by spectroscopic and chemical means to be 1-(O-α-D-glucopyranosyl)-3R,25R-hexacosanediol, 1-(O-α-D-glucopyranosyl)-3S,25R-hexacosanediol and 1-(O-α-D-glucopyranosyl)-3-keto-25R-hexacosanol.

Nonlinear effects and auto-induction in the asymmetric aldol condensation of synthetic equivalents of acetoacetic esters

Positive nonlinear effects, (+)-NLEs, have been detected in the Ti(IV)/BINOL complex-mediated catalytic asymmetric aldol reaction of three different masked acetoacetate esters. The use of a different procedure for the catalyst preparation disclosed the occurrence of aldol condensation of Chans diene through an auto-inductive process.