Synthesis of tritium labelled sparsomycin

The synthesis is described of tritiated sparsomycin (5), a broad-spectrum antitumor antibiotic, with high specific activity (31.4 Ci/mmol, 1.16 TBq/mmol). The radiolabel was introduced by reduction of the cysteine methyl ester 1 with lithium borotritide. 3H NMR analysis of the final product showed the concomitant formation of the mono- and ditritiated compound in a ratio of 2:1.