Methyl Isocyanate → 1-Hexadecylthio-2-methylcarbamoyloxy-3-trityloxypropane

To a solution of 1-hexadecylthio-3-trityloxy-2-propanol c1 4.6 g (8.0 mmol) in dichloromethane 100 ml are added 4-dimethylaminopyridine 1.17 g (9.6 mmol) and methyl isocyanate 4.72 ml (80 mmol). The solution is allowed to stand at room temperature for 72 hr and concentrated. The residue is chromatographed on SiO2 (46 g) and eluted with ethyl acetate:hexane (1:5) to give 1-hexadecylthio-2-methylcarbamoyloxy-3-trityloxypropane c2 as a crude oil (5.6 g). The oil is dissolved in dichloromethane 100 ml and boron trifluoride-methanol complex 1.68 ml (15.5 mmol) is added under cooling. The resulting yellow solution is stirred at 0° C. for 15 min and then at room temperature for 1 hr. Sodium carbonate aq solution is added to neutralize the reaction mixture and an organic layer is separated. The organic layer is subjected to SiO2 (80 g) column chromatography and eluted with ethyl acetate:hexane (1:1) to afford crude crystals 2.07 g. The crystals are triturated and washed with pentane to yield the titled compound V c1 1.205 g. The mother liquor is purified by Lobar column chromatography with the same solvent as described above to give additional V c1 0.321 g (49% total yield), mp. 53°-55° C.