1. Carbon-13-proton spin-spin coupling. 9. Purine
2. For reviews see (a) Carbon-Carbon and Carbon-Proton NMR Couplings (Methods in Stereochemical Analysis, Vol. 2) VCH, Deerfield Beach, FL (1983);
3. (b) Annu. Rep. NMR Spectrosc., edited by Academic Press, New York, 12, 82 (1982);
4. (c) Prog. Nucl. Magn. Reson. Spectrosc. edited by and Pergamon Press, Oxford, 14, 175 (1981);
5. (d) Prog. Nucl. Magn. Reson. Spectrosc. edited by and Pergamon Press, Oxford, 11, 1 (1977).