Armando Córdova

Proline-catalyzed asymmetric assembly reactions: enzyme-like assembly of carbohydrates and polyketides from three aldehyde substrates☆

Abstract Directed asymmetric assembly of simple achiral building blocks into stereochemically complex molecules like triketides has been described for the first time using l -proline catalyzed asymmetric double aldol reactions. The product pyranoses contain four asymmetric centers constructed under proline catalysis in a highly diastereoselective and modestly enantioselective fashion from three aldehyde molecules. These results suggest that the construction of complex products from simple starting materials is within the realm of organocatalysis involving the simple naturally occurring amino acid l -proline. Our successful assembly of pyranoses from simple aldehydes under proline catalysis suggests that this approach may warrant consideration as a prebiotic route to sugars and polyketides.

anti-Selective SMP-catalyzed direct asymmetric Mannich-type reactions: synthesis of functionalized amino acid derivatives

The first (S)-2-methoxymethylpyrrolidine (SMP)-catalyzed direct asymmetric Mannich-type reactions of unmodified aldehydes with N-PMP-protected α-imino ethyl glyoxylate are described. The reaction proceeded in a highly anti-selective manner (dr up to 19:1) with enantioselectivities between 74 and 92%.

Direct organocatalytic asymmetric Mannich-type reactions in aqueous media: one-pot Mannich-allylation reactions

The first direct organocatalytic asymmetric Mannich-type reactions in aqueous media are demonstrated herein. l-Proline-catalyzed reactions in aqueous media to provide β-formyl substituted α-amino acid derivatives with excellent diastereoselectivities (dr up to 19:1, syn/anti) and high enantioselectivities (ee between 72 and >99%). These conditions provided for the development of novel one-pot asymmetric syntheses of cyclic γ-allyl substituted α-amino acid derivatives (ee up to >99%). This was accomplished by combining the proline-catalyzed Mannich-type reactions with indium promoted allylations in aqueous media.

Convenient synthesis of L-proline benzyl ester.

Mesylates or tosylates of delta-hydroxy-L-norvaline esters spontaneously afford L-proline esters upon exposure to aqueous buffer in near quantitative yield. This novel reaction has led to the development of a simple route to optically active proline esters.