Esteban Domínguez

Enantioselective solution- and solid-phase synthesis of glutamic acid derivatives via Michael addition reactions

Abstract The enantioselective conjugate addition of Schiff base ester derivatives to Michael acceptors either in solution (56–89% e.e.) or on solid-phase (34–82% e.e.) gave optically active unnatural α-amino acid derivatives. The reaction was conducted in the presence of chiral, non-racemic quaternary salts derived from the cinchona alkaloids using neutral, non-ionic phosphazene bases.

A practical route to (E)-γ-hydroxy-αβ-unsaturated phenyl sulfones

Abstract Reaction of enolizable aldehydes with p-tolylsulfinylmethyl phenyl sulfone (1) in the presence of piperidine in acetonitrile gave selectively E-γ-hydroxy-αβ-unsaturated phenyl sulfones (2) in good yields. Reaction from enantiomerically pure sulfoxide 1 gave unsaturated sulfones 2 in moderate optical yields (ee= 10-50%).

Synthesis and conjugate additions to (E)-γ-alkoxy-α-substituted-α,β-unsaturated sulfones

Abstract (E)-γ-hydroxy-α,β-unsaturated sulfones have been readily functionalized at α-position via protection of hydroxyl group, metalation with n-BuLi and subsequent reaction with electrophiles. The conjugate addition of organolithiums to (E)-γ-methoxymethoxy-α-trimethylsilyl-α,β-unsaturated phenyl sulfones in Et 2 O is highly syn-stereoselective.

Stereoselective approach to optically pure syn 2-amino alcohol derivatives

Abstract A highly stereoselective procedure for the preparation of a variety of syn 2-amino alcohol derivatives from enantiopure E-γ-hydroxy-α,β-unsaturated phenyl sulfones is described. The method is based on an intramolecular carbamate cyclization, followed by functionalization at α-position by reaction of the sulfonyl carbanion with electrophiles, and subsequent elimination of the sulfonyl group.

Facile synthesis of E-γ-hydroxy-α,β-unsaturated sulfones from aldehydes

Abstract Reaction of enolizable aldehydes with p-tolylsulfinylmethyl phenyl sulfone (1), in the presence of piperidine in acetonitrile at O°C, gave selectively E-γ-hydroxy-α,β-unsaturated phenyl sulfones in good yields.

Diastereoselectivity of the conjugate addition of organocopper reagents to (E)-γ-hydroxy-α,β-unsaturated sulfones

Abstract The conjugate addition of organocopper reagents, mainly the higher order cuprates R3CuLi2, to (E)-γ-hydroxy-α,β-unsaturated phenyl sulfones takes place with excellent yields and high anti-selectivity.

Solid-phase synthesis of substituted glutamic acid derivatives via Michael addition reactions

Abstract The conjugate addition of Michael acceptors to the resin-bound benzophenone imine of glycine leads to a variety of racemic unnatural glutamic acid derivatives. This new approach expands the scope of unnatural amino acid and peptide synthesis (UPS).

An efficient preparation of optically active (E)-γ-hydroxy-α,β-unsaturated phenyl sulfones using lipase-mediated acylations

(E)-γ-Hydroxy-α,β-unsaturated phenyl sulfones have been efficiently resolved via irreversible enzymatic acylation with lipase PS (pseudomonas cepacia) and vinyl acetate. This process has been applied to the synthesis of the aggregation pheromone (−)-(3S,4S)-4-methyl-3-heptanol.

Flexible and stereoselective construction of polypropionate chains from enantiomerically pure γ-hydroxy-α,β-unsaturated sulfones

Abstract Following an homologation sequence the readily available enantiomerically pure γ-hydroxy vinyl sulfone 2 has been transformed, with complete control of the stereochemistry, into γ-hydroxy vinyl sulfones of polypropionate structure. The four stereotriads have been prepared by stereoselective additions of organometallics to the vinyl sulfone moiety and by stereoselective reduction of β-hydroxyketones. In a similar way, these triads are the substrates for the stereoselective introduction of the fourth consecutive asymmetric center.

1,3-Dipolar cycloaddition of enantiopure γ-oxygenated-α,β-unsaturated phenyl sulfones with nitrile oxides☆

Abstract The 1,3-dipolar cycloadditions of several enantiopure γ-oxygenated-α,β-unsaturated sulfones with acetonitrile and benzonitrile oxides have been studied. The reactions occurred at room temperature with moderate yields (31–65%), complete regioselectivity in favour of the isoxazolines with the phenylsulfonyl group at C-4, and moderate or high anti -stereoselectivity. After reductive elimination of the sulfonyl group and further reduction of NO bond, enantiomerically pure β-hydroxyketones or 1,3-aminoalcohols were obtained.