Resolution of optical isomers of 4-amino-p-chlorobutyric acid lactam by co-crystallization

4-Amino-p-chlorobutyric acid lactam crystallizes as racemic crystals in the monoclinic space group P2(1)/n, with a = 5.006(2), b = 6.783(2), c = 27.652(2) Angstrom, beta = 92.25(1)degrees, Z = 4, R = 0.035 for 1618 unique reflections. As both enantiomers are present in a single crystal it is not possible to effect enantiomeric separation by crystal growth inhibition. This lactam may, however, be co-crystallized with (2R,3R)-(+)-tartaric acid forming a 2:1 complex in which only the (R) enantiomer is present. The complex crystallizes in the monoclinic space group P2(1) with a = 10.074(2), b = 10.132(6), c = 12.238(6) Angstrom, beta = 99.13(2)degrees, Z = 2, R = 0.036 for 2291 unique reflections. Complex formation is effected by hydrogen bonding but enantioselectivity does not involve the chiral center of the title compound directly.