Table 1

Cycles used with trichloroacetimidate and phosphate donors.

StepFunctionReagentTime (min)
Trichloroacetimidate cycle
 1Couple10 equiv. donor and 0.5 equiv. TMSOTf30
 2WashDichloromethane6
 3Couple10 equiv. donor and 0.5 equiv. TMSOTf30
 4WashDichloromethane6
 5Wash1:9 methanol:dichloromethane6
 6Deprotection2 × 10 equiv. NaOMe (1:9 methanol:dichloromethane)60
 7Wash1:9 methanol:dichloromethane 4
 8Wash0.2 M acetic acid in tetrahydrofuran 4
 9WashTetrahydrofuran4
10WashDichloromethane6
Phosphate cycle
 1Couple5 equiv. donor and 5 equiv. TMSOTf30
 2WashDichloromethane6
 3Couple5 equiv. donor and 5 equiv. TMSOTf30
 4 Wash1:9 methanol:dichloromethane4
 5WashTetrahydrofuran4
 6Wash3:2 pyridine:acetic acid 3
 7Deprotection2 × 20 equiv. hydrazine (3:2 pyridine:acetic acid)30
 8Wash3:2 pyridine:acetic acid3
 9Wash1:9 methanol:dichloromethane4
10Wash0.2 M acetic acid in tetrahydrofuran4
11WashTetrahydrofuran4
12WashDichloromethane6