Scheme 2.
Reagents and conditions: (a) NaH, PMBCl, DMF, 0 °C, 81%; (b) NaIO4, OsO4, MeOH/H2O, then NaBH4, MeOH, 53%; (c) DAST, pyridine, CH2Cl2, 76%; (d) DDQ, CH2Cl2/H2O, 60%; (e) DIAD, TPP, Ad(Boc)2; (f) 3 N HCl/MeOH, 58% for two steps.
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