N-Acetoacetylation

The biosynthesis of tenuazonic acid was studied using [l-14C]-labeled acetate. N-acetoacetyl-L-isoleucine (7) was detected by radioactive trapping, indicating that amide formation, rather than carbon-carbon bond formation is probably the first step. None of the simple tetramic acid (8)... 

N-Acetoacety lotion. The N-acetoacetylation of amides with diketene is markedly improved if it is carried out in the presence of iodotrimcthylsilanc (generated in situ). The reactive reagent is probably a. 

E5, 525 (COOR COOH) N-Acetoacetyl- XV/1, 181 N-Acetyl-a-methyl- E21a, 836 5-Alk —5-CH3 —3-[CH(CH3) —Ar]—4-oxo—4,5-H2 — 3H-imidazol/ Hydrolyse + Ac20 a-subst. E16d, 410 (Hydrolyse) E21a, 828 [l-Acyl-3-alk(3,5-dialk)—2-tert.-butyl — 4-imidazoldin — 2-on/Hydroly-se]... 

N-Protection in peptide synthesis. Diketene reacts with an amino ester hydrochloride in ethanol at 0-5° in the presence of 1 equivalent of sodium ethoxide or a tertiary amine to give the often crystalline and easily purified N-acetoacetyl derivative (1). After peptide synthesis the protective group is removed by treatment with phenylhydrazine, which affords l-phenyl-3-methyl-5-pyrazolone. 

Heterocycies. The N-acetoacetyl derivative of an a-amino ester can be cyclized by base to an a-acetyltetramic acid." Biichi and Lukas used this sequence in the... 

N-Acetoacetyl derivatives of aromatic and aliphatic L-a-amino acids exhibit enantiomorphic CD spectra in ethanolic potassium hydroxide (Sabri et a/., 1977). It has been stated that this phenomenon might be due to conformational effects and/or to differences in the interaction between aryl and alkyl groups and the chromophore. Conformer A might be preferred for the aliphatic series and conformer B might prevail in the aromatic series (19 and 20, respectively). 

Mercuric acetate Mercuric salts as catalysts N-Acetoacetylation with diketene... 

Acetoacetic ester s. y -Keto-carboxylic acid esters C-Acetoacetylation with diketene 24,708 N-Acetoacetylation with diketene 24, 334, 708 Acetone as reagent (s. a. under Sensitizers) 22, 324 Acetonitrile... 

A reaction between o-toluidine and diketene yields N-acetoacetyl-2-toluidide, a base material for the production of pigments such as Pigment Yellow 14. 

Xylidine is used in the preparation of N-acetoacetyl-2,4-xylidide (AAX), an intermediate in pigment manufacture it is accessible by the reaction of 2,4-xyli-dine with diketene. 

N-Acetoacetylation with diketene of N-silylcarboxylic acid amides... 

A soln. of N-trimethylsilyl-2-pyrrolidone and diketene in dry benzene refluxed 4 hrs. in the presence of a catalytic amount of triethylamine, a little water added, and warmed 10 min. at 60° on a water bath -> N-acetoacetyl-2-pyrrolidone. Y 89%. F. e. and different reaction with silylated prim, amides s. Y. Yamamoto and H. Kimura, Chem. Pharm. Bull. 24, 1236 (1976). 

Galvez N, Moreno-Manas M, Sebastian RM, Vallribera A (1996) Dimethoxyethane as an alternative solvent for Schmidt reactions. Preparation of homochital iV-(5-oxazolyl) oxazolidinones from N-acetoacetyl derivatives of oxazolidinones. Tetrahedron 52 (5) 1609-1616... 

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