Reagents and conditions: (a)
R1–OH, NaOH, CHCl3, 0–40 °C,
25–50%; (b) 32, DMF/DCM (1:1), HATU, DIPEA, 45
°C, 12 h, 40–60%; (c) DCM, TMS-I, 0 °C, 5 h, (100%
crude yield); (d) DMF/DCM (1:1), HATU, DIPEA, 45 °C, 12 h, 40–80%;
(e) H2, Pd/C, EtOH; (f) final deprotection step and Chiralcel
OD column purification.