1-(1-Carboxy-methyl-1,4-anhydro-2,3-O-isopropyl-idene-α-d-erythrofuranos-yl)thymine.

X-Ray crystallography unequivocally determined the stereochemistry of the thymine base in the title compound, C(14)H(18)N(2)O(7). The absolute stereochemistry was determined from the use of d-ribose as the starting material. There are two independent mol-ecules in the asymmetric unit (Z' = 2) which exist as N-H⋯O hydrogen-bonded pairs in the crystal structure.