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. 2003 Dec 15;31(24):7175–7188. doi: 10.1093/nar/gkh154

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graphic file with name gkh154s1.jpg — Scheme 1. Conditions: (a) di-t-butyl dicarbonate, Et₃N, DMAP, 1,2-dichloroethane, 75°C, 1 h, 78%; (b) CH₃CN, n-BuLi, THF, –78°C, 1.5 h; (c) silica gel, 80°C, 2.5 h, 41% (two steps); (d) aqueous Na₂CO₃–EtOH, 90°C, 3.5 h, 86% (from 7 to 8); (e) TBAF, THF, 0°C–room temperature, 1 h, 75%; (f) aqueous Na₂CO₃–EtOH, 90°C, 3 h, 58% (from 9 to 1).

graphic file with name gkh154s2.jpg — Scheme 1. Conditions: (a) di-t-butyl dicarbonate, Et₃N, DMAP, 1,2-dichloroethane, 75°C, 1 h, 78%; (b) CH₃CN, n-BuLi, THF, –78°C, 1.5 h; (c) silica gel, 80°C, 2.5 h, 41% (two steps); (d) aqueous Na₂CO₃–EtOH, 90°C, 3.5 h, 86% (from 7 to 8); (e) TBAF, THF, 0°C–room temperature, 1 h, 75%; (f) aqueous Na₂CO₃–EtOH, 90°C, 3 h, 58% (from 9 to 1).