Frozen Chirality of Tertiary Aromatic Amides: Access to Enantioenriched Tertiary α-Amino Acid or Amino Alcohol without Chiral Reagent.

One of the fundamental and intriguing aspects of life is the homochirality of the essential molecules. In this field, the absolute asymmetric synthesis of α-amino acids is a major challenge. Herein, we report access, by chemical means, to tertiary α-amino acid derivatives in up to 96 % ee without using any chiral reagent. In our strategy, the dynamic axial chirality of tertiary aromatic amides is frozen in a crystal and is responsible for the stereoselectivity of the subsequent steps. Furthermore, we could control the configuration of the final product by manually sorting and selecting the initial crystals. Based on vibrational circular dichroism studies, we could rationalize the observed stereoselectivity.

Substrate control in enantioselective and diastereoselective aldol reaction by memory of chirality: a rapid access to enantiopure ß-hydroxy quaternary α-amino acids.

An asymmetric aldol reaction by memory of chirality is reported with a substrate control of stereoselectivity by aldehyde and rationalized. Starting from l-alanine, several diastereopure and enantioenriched ß-hydroxy quaternary α-amino acids have been obtained in three steps. The initial chirality of l-alanine is memorized through the dynamic axial chirality of tertiary aromatic amide.

Memory of chirality of tertiary aromatic amide: application to the asymmetric synthesis of (S)-α-methylDOPA.

We describe an original asymmetric synthesis of (S)-α-methylDOPA proceeding by the concept of memory of chirality, the only source of chirality being the starting D-alanine. The initial chirality of the amino acid is temporarily transferred to a dynamic axial chirality of a tertiary aromatic amide. The (S)-α-methylDOPA hydrochloride is obtained after four steps with 98% ee.

Synthesis and catalytic properties of 4-aryl-2,3-dihydro-4H-pyrimido[2,3-b]benzothiazoles for asymmetric acyl or carboxyl group transfer reactions.

4-Aryl-2,3-dihydro-4H-pyrimido[2,3-b]benzothiazoles (4-Ar-DHPBs) were synthesized and their catalytic activity and selectivity in kinetic resolution of a secondary alcohol as well as in the Steglich rearrangement and related reactions were evaluated. 4-Aryl-DHPBs showed low enantioselectivity in the acylative kinetic resolution of 1-phenylethanol. Conversely, they catalyzed the Steglich rearrangement with moderate to excellent enantioselectivity, demonstrating the possibility for remote stereocontrol by introduction of a substituent at the 4-position of DHPB.

Pyridine core activation via 1,5-electrocyclization of vinyl pyridinium ylides generated from bromo isomerized Morita-Baylis-Hillman adduct of isatin and pyridine: synthesis of 3-spirodihydroindolizine oxindoles.

An activation of the pyridine nucleus has been achieved via 1,5-electrocyclization of vinyl pyridinium ylides generated from bromo isomerized Morita-Baylis-Hillman adducts of isatin and pyridine under basic conditions. The method has been successfully applied for an efficient synthesis of a number of 3-spirodihydroindolizine-2-oxindoles, which have been found as core structure of secoyohimbane and heteroyohimbane alkaloid natural products.

Synthesis of novel functionalized 3-spiropyrrolizidine and 3-spiropyrrolidine oxindoles from Baylis-Hillman adducts of isatin and heteroaldehydes with azomethine ylides via [3+2]-cycloaddition.

A novel regioselective synthesis of a number of functionalized 3-spiropyrrolizidine and 3-spiropyrrolidine oxindoles from Baylis-Hillman adducts of isatin and heteroaldehydes via [3+2] cycloaddition of azomethine ylides in excellent yields has been reported.