TV-benzyloxycarbonyl

To a mixture of the TV-benzyloxycarbonyl-TV-methyl amino add 17 (1 mmol) and EtOH (30 mL) in a 100-mL round-bottomed flask was added 10% Pd/C catalyst (20 mg). The mixture was stirred at rt in an atmosphere of H2 until the required amount of H2 had been absorbed. The mixture was then taken to dryness. The residue was taken up in hot distilled H20 (15 mL) and filtered through Celite. The filter cake was washed with hot H20 (2 x 10 ml) and the combined filtrates were taken to dryness in vacuo to afford a white solid. The solid was then dissolved in the minimum of hot distilled water and crystallized by addition of EtOH to afford the pure TV-methyl amino acid. 

Reaction with Amino Alcohols and Related Compounds. Both secondary and tertiary carbamates bearing a vicinal hydroxyl group react with carboxylic acids in the presence of DEAD and TPP to afford the corresponding esters with inversion of configuration (eq 34). Reaction of N-t-butoxycarbonylserine with methanol, DEAD, and TPP gives the corresponding methyl ester in >98% yield (eq 35). Without methanol, TV-benzyloxycarbonyl- or A-f-butoxycarbonylserine reacts with the preformed adduct of DEAD and TPP to afford the P-lactone (eq 35). The W-protected serine methyl ester (37a) and threonine methyl ester (37b) react with DEAD and TPP to give the dehydrated products (38a) and (38b) (eq 36). ... 

W-Benzyloxycarbonyl-TV -methyl-L-alaninamide [33628-84-1 ] M 236.3. Recrystd from ethyl acetate. 

The carbodiimide method has been employed in several syntheses of depsipeptides. However, direct application of DCC for the formation of the ester bond between the amino acid and hydroxy acid components under the usual conditions of amide coupling affords the desired depsipeptides in acceptable yields only in the case of unhindered co-hydroxy units [54] or an active hydroxy group, such as in TV-benzoyl-u-hydroxyglycine benzyl ester. For example, Ravdel et al.[55 have performed the esterification of various benzyloxycarbonyl- and phthalylamino acids with /V-benzoyl-a-hydroxyglycine benzyl ester with DCC in 50-65% yield. On the other hand, Shemyakin et all21 failed to obtain the expected depsipeptide products on condensation of bulky benzyloxycarbonyl- or phthalylvaline with a-hydroxy-isovaleric acid benzyl ester. The main product was acylurea in the first case and phthalylvaline anhydride in the second. Thus, the classical carbodiimide procedure could not be applied in practical depsipeptide preparation. 

Enantiomerically pure, unprotected tetramic acids are accessible by hydrogenolytic deprotection of 4-(benzyloxycarbonyl)amino-3-oxocarboxylic esters 31 (X= Z Y = H) followed by ring closure (Scheme 11)J55 In the absence of TV-carbamate protection, the next reduction step is not totally stereoselective/54 ... 

Hie most used synthetic substrates are jV-benzoyl-L-Aig-ethyl ester (BAEE), TV-benzoyl-L-Aig-amide (BAA), Af-benzyloxycarbonyl-Lys-p-nitrophenyl ester, jV-benzoyl-L-Arc-p-nitroanilide (L-Bapa). toavl-L-Arg-methyl ester (TAME). /V-benzoyl-L-Aig-methyl ester (BAME), Gly-ethyl eater, His-ethyl ester, benznyl-Gly-ethyl eater, L-Leu-p-mtroanilide (Leupa), L-Ala-p-nitroanilide (Alapa),... 

An efficient method of resolution of diastereomeric mixtures of 5-substituted 2-oxazolidinones, utilizing commercially available (S)-l-phenylethylamine as the optically active portion of the molecule, has been developed16. Thus, the Ar-benzyloxycarbonyl derivative of (S)-TV-(l-phen-ylethyl)-2-propen-1-amine (1), treated with iodine in chloroform, affords the diastereomeric products as a 50 50 mixture which is easily separated by chromatography on silica gel. 

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