Latent inhibitors. Part 9. Substrate activated time-dependent inhibition of carboxypeptidase A by aminocyclopropanecarboxylic acid derivatives and analogues

Evaluation of Solution and Solid-Phase Approaches to the Synthesis of Libraries of α,α-Disubstituted-α-acylaminoketones

“…The key Weinreb amide intermediates 44 were generated by opening the azlactone rings of 43 with N,O-dimethylhydroxylamine in the presence of pyridine. 37 Treatment of 44{6,6} with 3-methoxy-phenylmagnesium bromide 6{7} in THF at room temperature afforded the desired R-acylaminoketone 2{6,6,7} in 63% yield. However, when the Grignard reaction was performed with the more sterically congested Weinreb amide 44{3,6} under similar conditions, the major product was N-(hydroxymethyl)-N-methylamide 45{3,6} and little of the desired ketone 2{3,6,7} was present in the crude reaction mixture.…”

“…Commercially available α,α-disubstituted amino acids 4 { 2 }, 4 { 3 }, and 4 { 6 } were cyclized to the corresponding azlactones 43 { 2,6 }, 43 { 3,6 }, and 43 { 6,6 } by treatment with 2.5 equiv of the acid chloride of 2-methyl-3-methoxybenzoic acid 5 { 6 } in pyridine. The key Weinreb amide intermediates 44 were generated by opening the azlactone rings of 43 with N , O -dimethylhydroxylamine in the presence of pyridine . Treatment of 44 { 6,6 } with 3-methoxy-phenylmagnesium bromide 6 { 7 } in THF at room temperature afforded the desired α-acylaminoketone 2 { 6,6,7 } in 63% yield.…”

Mechanistic Studies on Phosphopantothenoylcysteine Decarboxylase: Trapping of an Enethiolate Intermediate with a Mechanism-Based Inactivating Agent

“…The final product was dissolved in H 2 O, titrated to pH ∼6.5 with 1 M NaOH, and stored as frozen aliquots of a stock solution (100 mM) at -20 °C. 1 4′-Phosphopantothenate (30). Benzyl pantothenate 4′-O,Odibenzyl phosphate (36) (419 mg, 736 mmol) was dissolved in 4.4% formic acid in methanol (21 mL), and palladium black (210 mg) was added.…”

“…For example, the nucleophilic ring opening of the cyclopropyl group of 1-amino-1-cyclopropanecarboxylic acid (ACC) occurs when the substrate is activated by imine formation with a pyridoxal cofactor in a reaction catalyzed by ACC deaminase (19)(20)(21)(22). Activated cyclopropyl-containing substrate analogues are also used as electrophilic traps in a wide variety of enzyme-catalyzed reactions (23)(24)(25)(26)(27)(28)(29)(30)(31)(32), while nucleophilic ring opening of cyclopropanes substituted with two ester groups has been extensively used in organic synthesis (33). In all these cases, the ring-opening reaction is driven by the strain in the cyclopropyl ring and by the stabilization of the resulting carbanion by electron-withdrawing substituents (such as esters or aldehydes) on the ring.…”

Stereochemistry in Inactivation of Carboxypeptidase A. Structural Analysis of the Inactivated Carboxypeptidase A by an Enantiomeric Pair of 2-Benzyl-3,4-epoxybutanoic Acids

“…Carboxypeptidase A (CPA, EC 3.4.17.1) is a well studied zinc containing proteolytic enzyme and has received much attention as it represents a large family of zinc containing metalloenzymes of physiological importance − Recently, we have reported that 2-benzyl-3,4-epoxybutanoic acid (BEBA) is a pseudomechanism-based inactivator of CPA designed rationally making use of the unique property of the active site zinc ion: as for being a Lewis acid, the zinc ion activates the scissile amide bond of substrate for catalytic nucleophilic attack 5d.…”