... 1. Heterocyclic Chern., 18, 893 (1981). ... J,',”, J4'5', JZ'oHa', J,',,' JS',,,' J,s. JNHCH3 ... Therefore 18a and 186 have been unambiguously identified by the measurement of the relaxation times of ribose protons (Table I). Further- more chemical shift assignments of the different protons ...