To a solution of benzyl 4-mercapto-2-methylbutan-2-ylcarbamate (242 mg, 0.955 mmol) in N,N-dimethylformamide (1 ml) was added (1,4,7,10-tetraoxacyclododecan-2-yl)methyl 4-methylbenzenesulfonate (218.4 mg, 0.6060 mmol) and cesium carbonate (253 mg, 0.776 mmol). The solution was heated to 60° C. for 15 hours, cooled to room temperature, concentrated in vacuo, and the residue purified by flash chromatography (30%-100% ethylacetate in hexanes) to afford the title compound as a clear oil (quantitative); LRMS (ESI/APCI) m/z 442 [M]+.
