Scheme 3.
Reagents and conditions: a) Boc-L-isoleucine, HOBt, EDC, DIPEA, CH3CN; b) HCl, CH3OH; c) BH3 • S(CH3)2; d) Boc-7-hydroxy-D-Tic-OH, EDC • HCl, DIPEA, HOBt, THF; e) HCl, CH3CN, dioxane.
Reagents and conditions: a) Boc-L-isoleucine, HOBt, EDC, DIPEA, CH3CN; b) HCl, CH3OH; c) BH3 • S(CH3)2; d) Boc-7-hydroxy-D-Tic-OH, EDC • HCl, DIPEA, HOBt, THF; e) HCl, CH3CN, dioxane.