Figure 3: Synthesis of (2R,3R,4R)-Fmoc-D-allo-AHDMHA-OH.
From: The first total synthesis of the cyclodepsipeptide pipecolidepsin A
(a) i. 2-bromo-3-methyl-2-butene, tBuLi, Et2O, −78 °C, 3.3 h; ii. Garner’s aldehyde 12, Et2O, −78→25 °C, 1.2 h, 36%; (b) H2 (4 atm), Pd-C (10%), MeOH, 25 °C, 2 days, 78%; (c) 2,6-di-tert-butyl pyridine, Tf2O, DCM, 0 °C, 10 min, 90%; (d) i. Jones reagent, acetone, 0 °C, 15 h; ii. Diazomethane, Et2O, 67%; (e) Concentrated HCl, reflux, 72 h, 100%; and (f) Fmoc-OSu, Na2CO3, H2O−dioxane (1:1), 25 °C, 15 h, 91%.
