Aminoalcohols, esterification

Triflic acid has been used in the selective esterification ( (9-acylation) of a series of aminoalcohols in the presence of a crown ether (DB24C8) to prepare rotaxanes.900 The test reaction of diethanolamine with bulky anhydride, crown ether, and triflic acid (molar ratio = 1 2 2 1.5) gave the rotaxane 276 in high yield in a clean reaction [Eq. (5.327)]. /V-Arylmethylaminoalcohols were similarly transformed (85-92% yields). 

Optically active allylboronates bearing chiral auxiliary located at the boron atom found widespread applications in asymmetric synthesis. Enantiomerically enriched a-alkylidene-y-lactones and lactams can also be synthesized following such a synthetic approach. VUlieras et al. (41, 45] demonstrated the potential of chiral allylboronates derived from 2-phenyl-2,3-bomanediol, ephedrine, or norephedrine for this purpose. Chiral allylboronates 46a,b were obtained in a sequence of reactions involving transformation of achiral precursors 32 into the corresponding boronic acids 44 followed by their esterification with enantiomerically pure diol or 1,2-aminoalcohol 45 (Scheme 4.10). In the case of methyl-substituted derivatives 32b (R = Me), initial composition of E- and Z-isomers was transferred to the target allylboronates 46b. Importantly, the isomeric mixture was separated by means of the column chromatography. 

Direct esterification of aminoacids and araino..v,id halides. Other preparat+ons of esters of aminoacids. Esters of aminoalcohols. 

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