Enantiomerically pure P-chiral dicyclohexylammonium 2-(phosphinyl)acrylates as new Michael acceptors. Enantioselective synthesis of α-methylene-δ-valerolactones

A convenient method for the preparation of enantiomerically pure P-chiral dicyclohexylammonium 2-(phosphinyl)acrylates 6 and 7 is presented. The synthesis of α-methylene-δ-valerolactone 5a with enantiomeric excesses of 85% and 80% has been developed. The key step of the synthesis involves an asymmetric Michael addition of imine 10 to acrylates 6 and 7, respectively.

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(R)-2-[Methoxy(phenyl)phosphoryl]acrylic acid, dicyclohexylammonium saltC22H34NO4PEe = 99%[α]D = −14.1 (c 0.57, CHCl3)Source of chirality: optical resolutionAbsolute configuration: (R)

(R)-2-[Ethoxy(phenyl)phosphoryl]acrylic acid, dicyclohexylammonium saltC23H36NO4PEe = 99%[α]D = −14.4 (c 1.06, CHCl3)Source of chirality: optical resolutionAbsolute configuration: (R)