Sodium Bicarbonate → S-Ethyl O-(N3,N7,N12,N16-tetra(t-butoxycarbonyl)-3,7,12,16-tetraazahexadecanoyl oxy)methyl carbonothioate

Participants

Reaction Steps

S-Ethyl O-iodomethyl carbonothioate (423 mg, 1.72 mmol) was added to a stirring mixture of 31 (1.13 g, 1.71 mmol), NaHCO3 (298 mg, 3.55 mmol) and tetrabutylammonium hydrogensulfate (588 mg, 1.73 mmol) in CH2Cl2/H2O (1:1, 17 mL) and the resulting mixture was stirred at room temperature overnight. The reaction mixture was diluted with CH2Cl2 (80 mL) and the aqueous layer was discarded. The organic layer was washed with saturated aqueous NH4Cl, saturated aqueous NaCl, dried over Na2SO4 then concentrated under reduced pressure. The residue was resuspended in Et2O, filtered and again concentrated under reduced pressure. The crude material was purified by silica gel chromatography (25%-60% EtOAc in hexanes over 10 column volumes) to give the colourless liquid 32 (1.23 g, 92%): 1H NMR (400 MHz, CDCl3): δ 1.32 (t, J=7.3, 3H), 1.41-1.47 (m, 40H), 1.61-1.75 (m, 4H), 2.89 (q, J=7.3, 2H), 3.10-3.31 (m, 12H), 3.92 (s, 4/7 of 2H, rotamer A), 4.01 (s, 3/7 of 2H, rotomer B), 5.84 (s, 2H).

Provenance & Evidence