Pyridine → (2'S,3'R,4'S,5'R,6'R)-3',4',5'-tris(benzyloxy)-6'-(benzyloxymethyl)-8-chloro-7-(4-ethylbenzyl)-3,3',4,4',5',6'-hexahydro-2H-spiro[benzo[b]oxepine-5,2'-pyran]

Participants

Reaction Steps

To a solution of 35 (115 mg, 0.139 mmol) and pyridine (100 μL) in DCM (1 mL) was added methanesulfonic anhydride (44 mg, 0.25 mmol, 1.8 equiv). The resulting mixture was stirred at ambient temperature for 1 hour. LC/MS analysis indicated complete conversion of 35 to mono mesic ester 36. The reaction mixture was partitioned between 10% sodium bicarbonate and DCM, after which the organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to obtain a residue which was heated in DMF (3 mL) containing potassium carbonate (100 mg) at 90° C. for 0.5 hours. The resulting mixture was extracted with DCM, after which the organic layer was separated, dried (Na2SO4), filtered, and evaporated. Preparatory TLC of the residue eluting with 12% ethyl acetate in petroleum ether gave 37 (62 mg, 55% yield). 1H NMR (300 MHz, CDCl3) δ 7.54 (s, 1H), 7.16-7.28 (m, 21H), 7.08-7.11 (m, 2H), 6.98 (m, 4H), 6.97 (s, 1H), 4.81 (d, J=11.1 Hz, 1H), 4.77 (d, J=10.8 Hz, 1H), 4.73 (d, J=10.8 Hz, 1H), 4.47-4.60 (m, 3H), 4.35 (d, J=10.5 Hz, 1H), 4.16-4.24 (m, 1H), 3.70-4.02 (m, 11H), 2.60-2.71 (m, 1H), 2.54 (q, J=7.5 Hz, 2H), 2.02-2.13 (m, 1H), 1.81-1.93 (m, 2H), 1.16 (t, J=7.5 Hz, 3H). LC/MS m/z 832 (M+Na), 810 (M+H).

Provenance & Evidence