N-ALPHA-BOC-(+/-)-2,3-DIAMINOPROPIONIC ACID

White crystal

Diisopropylethylamine (120 uL, 0.691 mmol) was added to a solution of N10-Methyl-4-amino-4-deoxypteroic acid (75 mg, 0.23 mmol), HATU (88 mg, 0.23 mmol) in DMF (5 mL) and stirred at 23 C for 15 minutes (solution A). In another flask Compound (32-a) (47 mg, 0.23 mmol) was dissolved in DMSO (5 mL) and added Diisopropylethylamine (120 uL, 0.691 mmol) (Solution B ). Solution B was added to solution A via cannula and stirred the content for 1 h. Upon completion the reaction mixture was purified by preparative HPLC using C18 column. (2- carboxyethyl)triphenylphosphonium bromide (121 mg, 0.337 mmol) in DMF (3.5 mL). The reaction content was stirred at 23 C for 1 h. Upon completion, the reaction mixture was added to ether (500 mL) and precipitated solid was filtered and dried under high vacuum to obtain compound (53) as thick oil.General procedure: The desired Boc-protected amino acid 4 (2.2 mmol, 1 equiv) was dissolved in CH2Cl2 (2 mL) and a solution of HCl in 1, 4-dioxane (4 M, 2 mL) was added. The mixture was stirred at r.t. for 20-60 min and then the solvent was evaporated to dryness. To the resulting crude HCl acid salt (or commercial General procedure: The desired Boc-protected amino acid 4 (2.2 mmol, 1 equiv) was dissolved in CH2Cl2 (2 mL) and a solution of HCl in 1, 4-dioxane (4 M, 2 mL) was added. The mixture was stirred at r.t. for 20-60 min and then the solvent was evaporated to dryness. To the resulting crude HCl acid salt (or commercial