Aziridine-2-carboxylic acid methyl ester

The unactivated aziridine-2-carboxylic acid methyl ester was found to react with two molecules of aromatic thiol47 Initial ring opening is followed by a faster reaction (since little mono substitution product is found), probably involving formation of an episulfonium ion which is then ring opened by the second ArSH. The same result... 

Aziridine-1-carboxylic acid, methyl ester AGf , 7, 52 <71MI50400)... 

An asymmetric s)mthesis of 5-isopropyloxazoline-4-carboxylic acid methyl ester (164) was performed through the ring expansion on N-acylaziridine (163). The synthesis started from 4-methylpentenoyl imidate 161 that underwent 1,4-addition of 0-benzylhydroxylamine. Ring closure, activation of the aziridine and final ring expansion catalysed by BF3.Et20 afforded the desired compound <01TA563>. 

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-... 

Starting from ethyl 4, 4, 4-trifluorocrotonate, racemic aziridine carboxylic acid 96 was prepared as shown in Scheme 9.22 [46] and was then subjected to lipase-catalyzed esterification. Methyl ester 97 was obtained in 35% yield with excellent enantiomeric purity. Acid-catalyzed ring opening of aziridine 97 proceeded regio- and stereoselectively, affording 2-substituted (2R,3R) or (2/ ,3S)-3-amino-4,4,4-trifluorobutanoates 98 in high yields [47]. 

Aziridine-2-carboxylic acid, 3-methyl-, methyl ester H NMR, 7, 51 <6630 0390)... 

The key intermediate in the preparation of derivatives suitable for peptide synthesis (Table 3) is the benzyl (25)-7V-tritylaziridine-2-carboxylate, since it is smoothly converted into the N-protected imino acid by catalytic hydrogenolysis.[47] Similarly, the related methyl ester is saponified by lithium hydroxide to produce A-tritylaziridine-2-carboxylateJ83 84 Detrit-ylation to benzyl (2S)-aziridine-2-carboxylate is more difficult, but the dibenzosulfimide salt is found to be perfectly stable on storage as a solid for longer periods of time (see Section 9.2.1.1) J47l In solution, upon addition of bases the benzyl ester is sufficiently stable to allow for peptide syntheses.[47]... 

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). ... 

Aziridine carboxylates are chiral intermediates for the synthesis of -lactams and amino acids [200]. The use of enantioselective ester hydrolysis in the synthesis of optically active A -unsubstituted and A-substituted aziridine carboxylate by Candida cylindraceae lipase has been demonstrated by Bucciareli et al. [199]. Racemic methyl aziridine-2-car-boxylate and 2,3-dicarboxylate 110 were used as substrates both for enzymatic hydrolysis and for the synthesis of AAchloro, iV-acyl and A-sulfonyl derivatives (Fig. 38). The reaction yield of 35-45% (theoretical maximum yield is 50%) and the e.e. s of 90-98% were obtained depending on substrate used in the reaction mixture. 

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