A novel approach to 2,4-ethanoproline

A novel approach to 2-azabicyclo[2.2.1]heptane-1-carboxylic acid (2,4-ethanoproline) is reported starting from (2S,4R)-4-hydroxyproline. The synthetic scheme consists of 10 steps and results in 22% total yield of the title compound. Enantiomeric purity of the product is checked by chiral stationary phase HPLC.

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2-Benzyl 1-methyl 2-azabicyclo[2.2.1]heptane-1,2-dicarboxylateC16H19NO4Ee = 75%[α]D = +5.0 (c 0.034, CHCl3)Source of chirality: 4-hydroxyprolineAbsolute configuration: (1R,4S)