(2R,4R)-1-(tert-But-oxy-carbon-yl)-4-meth-oxy-pyrrolidine-2-carb-oxy-lic acid.

In the title compound, C(11)H(19)NO(5), the five-membered pyrrolidine ring adopts an envelope conformation. The dihedral angles between the carboxyl group plane, the pyrrolidine ring and the meth-oxy group are 59.50 (3) and 62.02 (1)°, respectively. In the crystal, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into chains along [100]. The absolute configuration is assigned in accord with that of (2R,4R)-1-(tert-but-oxy-carbon-yl)-4-hy-droxy-pyrrolidine-2-carb-oxy-lic acid, which was the starting material in the synthesis.