Scheme 3:
(a) MeOH/HCl; (b) Ac
2
O/Py; (c) AcCl, MeOH/CHCl
3
; (d) Ag
2
CO
3
/AgOTf, CH
2
Cl
2
, MS 4Å; (e) MeONa/MeOH; (f) NaOH/H
2
O; (g) CF
3
COOH.
