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. 2012 Feb 27;55(6):2549–2560. doi: 10.1021/jm201517a

Scheme 5.

Scheme 5

Reagents and conditions: (a) LiOH 1 M aq, THF/MeOH/H2O 3:1:1, 0 °C 30 min, room temp, 3 h (95 and 99%); (b) l-Pro-NH2, EDC, HOBt, Et3N, dichloromethane, room temp, 16 h (82% and 78%); (c) (i) H2, Pd/C, ethanol, room temp, 24 h, (ii) TFA, room temp, 4 h (quant yields over two steps); (d) (i) TFA, room temp, 16 h, (ii) Boc-l-Leu × H2O, EDC, HOBt, dichloromethane, molecular sieves, Et3N, room temp, 15 h (64% and 90% over two steps); (e) (i) H2, Pd/C, ethanol, room temp, 48 and 24 h, (ii) TFA, room temp, 4 h (72% and 73% over two steps).