Protection of Carboxyl Groups Esterification

FIGURE 3.18 Protection of carboxyl groups by esterification of amino acids (A) by acid-catalyzed reaction with alcohol. [Curtius 1888, Fisher 1906] with X = Cl for H-Xaa-OMe, X-Xaa-OEt, and H-Pro-OCH2Ph  

X = d-MeC SOj for H-Xaa-OCH2Ph 49 X = V2S04 for H-Xaa(OR5)-OH 12 and (B) by thionyl chloride-mediated reaction with methanol.48 

FIGURE 3.19 Dean-Stark water separator. Water is removed from the reaction medium by covaporization with benzene. 

M Brenner, W Huber Determination of a-amino acids through alcoholysis of the methyl ester, f/eiv ChimActa 36, 1109, 1953. 

JD Cipera, RW Nicholls. Preparation of benzyl esters of amino acids. Chem Ind (London) 16, 1955. 

---