Scheme 8.

Synthesis of 5(R)-C-phenyltetrahydrofurane derivative 81.

Reagents and Conditions: (i) Reference [21]; (ii) PhMgBr, THF, −78 °C then flash chromatography, 88%; (iii) (a) HCl (3N), MeOH, rt; (b) TBDMSOTf, pyridine, THF, 0 °C, 89% for the two steps; (iv) (a) DIBAL-H, CH₂Cl₂, −78 °C; (b) Ac₂O, pyridine, rt, 62% for the two steps; (v) TMSSPh, BF₃.OEt₂, hexane, −95 °C to rt, 89%; (vi) Bis-TMS-thymine, NBS, 4-A molecular sieve, CH₂Cl₂, −78 °C to −26 °C, 87%.