D benzyl ester

Alcalase selectively catalyses the hydrolysis of D,L-amino add methyl and benzyl esters to provide L-amino adds and D-amino add esters with high optical purity (Figure A8.10). 

L Olonyl-D-isoglutominyl-N -(benzyl-oxycorbonyl)-L-ly3ine benzyl ester (III)... 

C3H9NO 2749-11-3) see Ergometrine Levofloxacin L-alanyl-D-isoglutaminyl-7V -(benzyloxycarbonyl)-L-lysine benzyl ester... 

The pronounced proclivity of phosphoric monoester monoanions to eliminate POf is not always recognizable from the characteristic pH profile of Fig. 1. The hydrolysis rate maximum at pH w 4 may be masked by a faster reaction of the neutral phosphoric ester, as in the case of a-D-glucose 1-phosphate63) or on hydrolysis of monobenzyl phosphate 64). In the latter case, the known ability of benzyl esters to undergo SN1 and SN2 reactions permits fast hydrolysis of the neutral ester with C/O bond breakage. The fact that the monoanion 107 of the monobenzyl ester is hydrolyzed some 40 times faster than the monoanion 108 of the dibenzyl ester at the same pH again evidences the special hydrolysis pathway of 107, rationalized by means of the metaphosphate hypothesis. 

Benzylic esters, aroma chemicals, 3 256 Benzylideneacetone, 3 595 4,6-O-Benzylidene-D-glucopyranose,... 

Schultheiss-Reimann and Kunz(43) applied silver triflate as the promoting reagent for the reaction of 2,3,4-tri-O-benzyl-a-D-glucopyranosyl bromide (52) with V-(9-fluorenylmethoxycarbonyl)-L-serine benzyl ester to... 

Kenne and associates (57) have applied this procedure for the synthesis of a-D-mannopyranosyl derivatives linked to L-serine/L-threonine (59 and 60). Compounds 59 and 60 were obtained by coupling 2,3,4,6-tetra-<9-acetyl-D-mannopyranosyl chloride (56) with Fmoc-L-serine benzyl ester or Fmoc-L-threonine benzyl ester in the presence of silver triflate and 4-A molecular sieves, followed by deprotection (57). 

In a specific exception to Jones and Kirby s generalization, Tidwell found that the benzylic ester [120] has a shorter C-OX bond [1.457 A (A. D. Allen et al., 1987)] than cyclohexyl p-toluenesulphonate, even though the latter tosylate is solvolysed 200 times more slowly in trifluoroacetic acid. In this... 

D Ben-Ishai. The use of hydrogen bromide in acetic acid for the removal of car-bobenzoxy groups and benzyl esters of peptides. J Org Chem 19, 62, 1954. 

FIGURE 5.16 Production of amides by cleavage of benzhydryl amides. Recognition that removal by acidolysis of benzhydryl protectors from carboxamides gave the amides (B) led to development of benzhydrylamine (BHA) resin (C).33 Treatment with HF of a peptide amide that has been assembled on a BHA resin using Boc/Bzl chemistry gives the peptide amide (D). Peptide amide is also obtainable by ammonolysis of the resin-bound benzyl ester (A), a reaction that is more efficient if gaseous NH3 is employed (see Section 8.3). 

The use of Trt-protected 3-iodoalanines for lanthionine synthesis is also a highly promising method for the synthesis of 3-methyl- and 3,3-dimethyllanthionines. 40 This method is based on the use of A-trityl-3-iodoalanine benzyl ester (54) and the symmetrically protected bis(Boc)-cystine-derivative dimethyl esters derived from L-t/treo-3-methylcysteine and d-penicillamine. Yields of the respective lanthionine derivatives are >80% however, enantiomeric excesses have not been determined for the 3-substituted lanthionines (Scheme 18). 

V"-Fluoren-9-ylmethoxycarbonyl-3-0- 2-acetamido-2-deoxy-3,4-0-isopropyKdene-6-0-[methyl(5-acet-amido-4,7,8,9-tetra-0-acetyl-3,5,-dideoxy-D-glycero-a-galacto-2-nonulopyranosyl)onate]-a-D-galacto-pyranosylJ-L-threonme Benzyl Ester (84) 11251... 

S Additional information <9, 15, 17, 18, 21, 24, 30, 33, 35> (<18> activity is regulated by light [28] <30> D-aspartate, L-glutamate and -alanine are inactive as substitutes for L-aspartate in the forward reaction, in the reverse reaction ADP cannot be replaced by AMP, UDP, GDP or IDP [1] <17> aspartokinase III, o-isomers of the derivatives of aspartic acid, including D-aspartate cr-benzyl ester and o-aspartate /)-hydroxamate are not substrates regardless of whether the a- or the -carboxyl group is derivatized, L-cysteine sulfinate and 2-methyl-DL-aspartate are no substrates... 

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