Aziridinecarboxylic esters

Although this variant often gives yields of less than 50%, it is a general method for the preparation of aziridines, especially of aziridinecarboxylic esters such as 7. 

Treatment of aziridinecarboxylic esters having an electron-withdrawing substituent at nitrogen with acetonitrile under BF3 catalysis leads to a smooth ring expansion reaction as depicted in Scheme 28 [31]. 

The enolates of aziridinecarboxylic esters behave very much like unstabilised organolithiums - they are configurationally stable organolithiums - and as such, not surprisingly react with retention of stereochemistry. Aziridine 9 was proved to react via 10 with retention with benzyl bromide other electrophiles react stereospecifically, presumably with retention.14... 

Amines via condensations. Tryptophan derivatives are obtained by reaction of indoles with A-substituted aziridinecarboxylic esters at 0° or room temperature. Stoichiometric amount of Sc(OTf)3 is required. By SclOTfjj catalysis the Strecker-type synthesis from aldehydes, amines, and BujSnCN can be carried out either in organic solvents or in water. Pictet-Spengler reaction is directly accomplished using acetals. ... 

Aziridines. The reaction of a-imino esters with diazoalkanes provides aziridinecarboxylic esters. A copper(l) complex can also be used. 

Aziridine, 2,3-diphenyl-l-(2,4,6-trinitrophenyl)-irradiation, 7, 61 Aziridine, 1,2-divinyl-rearrangement, 7, 539 Aziridine, 2,3-divinyl-rearrangement, 7, 42, 65, 539 Aziridine, N-ethyl-inversion, 7, 6 Aziridine, 2-halo-reactions, 7, 74 Aziridine, A/-halo-invertomers, 7, 6 Aziridine, 2-methyl- N NMR, 7, 11 Aziridine, methylene-ring-ring valence isomerizations, 7, 22 synthesis, 7, 92 Aziridine, iV-nitroso-reactions, 7, 74 Aziridine, iV-phosphino-inversion, 7, 7 Aziridine, 1-phthalimido-UV irradiation, 7, 62-63 Aziridine, l-(3-thienyl)-2-vinyl-rearrangement, 4, 746 Aziridine, 7V-trimethylsilyl-inversion, 7, 7 Aziridine, 1,2,3-triphenyl-irradiation, 7, 61 Aziridine, vinyl-isomerization, S, 287 Aziridinecarboxylic acid ring expansion, 7, 262 Aziridine-2,2-dicarboxylic acid, 1-methoxy-diethyl ester... 

Cydization of P-hydroxy-a-amino esters under Mitsunobu reaction conditions is an alternative approach to aziridine-2-carboxylic esters [6b, 13-16], In this case the P-hydroxy group is activated by a phosphorus reagent. Treatment of Boc-a-Me-D-Ser-OMe 13 (Scheme 3.5) with triphenylphosphine and diethyl azodicarboxylate (DEAD), for example, gave a-methyl aziridinecarboxylic acid methyl ester 14 in 85% yield [15]. In addition to PPh3/DEAD [13b, 15], several other reagent combi-... 

Aziridine esters are a- and -amino acid derivatives at the same time. A characteristic reaction of a-amino acids is their reaction with triethylboron to give boroxazolidines. We showed that aziridinecarboxylic acids exhibit the expected behavior in their reaction with triethylboron, viz., that they form stable boroxazolidines 34 (Scheme 19) [29]. These boron heterocycles can be reconverted into the free amino acids by treatment with 8-hydroxyquinoline. 

An interesting synthesis of T-vinyl-l,2,3-dithiazolylimines 94 from Appel salt 20 and aziridines has been described <2005H(65)1601>. This procedure involves elimination of hydrogens from different nitrogen and carbon atoms. The reaction with aziridinecarboxylic acid ester or its amide 95 having the frarcr-configuration produces one of the possible... 

Nonracemic phenylserine derivatives can be prepared by the addition of ammonia to a,/ -di-halocarboxylic acid esters via aziridines59. Treatment of (li )-menthyl 2,3-dibromo-3-phenyl-propanoate (7) with methanolic ammonia proceeds stereoselectively to give a readily separable mixture of the diastereomeric and thermodynamically more stable (17 )-menthyl a s-3-phenyl-2-aziridinecarboxylates (8A and 8B) as crystalline solids59. 

Interestingly, the ring opening of 2-aziridinecarboxylic acid methyl ester 79 by a number of aromatic thiols under solvent-free and noncatalytic conditions resulted in the formation of bis-arylsulfanyl propanoic acid esters 82. Since only traces of the monosubstituted compound 80 were occasionally found in the crude reaction mixture, it would... 

Sodium enolates of ketones and disodium enediolates of substituted phenylacetic acids reacted with activated aziridines to afford 7-amido ketones and 7-amidobutyric acids, respectively (Scheme 72). Aziridine-2-carboxylic acid esters can be utilized as versatile precursors for amino acid derivatives. Although the product distribution resulting from the reaction of activated aziridine-2-carboxylates with amines depends on the structure of the reactants, the reactions with alcohols or thiols in the presence of acidic cabilysts generally gave the a-amino acid derivatives (Scheme 73). ° On the other hand, free 3-methyl-2-aziridinecarboxylic acids (168) reacted with thiophenol, cysteine and glutathione to afford P-amino acid derivatives with sulfur substituents at the a-position as the main product (Scheme 73). ... 

Serine has been prepared by a simple process in high yield through N-unsubst. 2-aziridinecarboxylic acid esters... 

Ring-opening of aziridinecarboxylic acids has been used in the conversion of threonine into /Areo-3-methylcysteine and in the synthesis of p-alkoxy-a-amino-acids. Improved methods have appeared for the synthesis of iV-(phosphono-acetyl)-amino-acids and for the preparation of y-esters of glutamic acid and (3-esters of aspartic acid. The protected P-hydroxy-a-amino-acids (278) are converted into a-fluoro-P-amino-acids (279) with DAST (Scheme 137). ... 

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