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Curtius rearrangement amino acids

A third approach to 3-amino-/3-lactams is by Curtius rearrangement of the corresponding acyl azides. These are readily prepared from r-butyl carbazides, available via photochemical ring contraction of 3-diazopyrrolidine-2,4-diones in the presence of f-butyl carbazate (c/. Section 5.09.3.3.2). Thus treatment of (201) with trifluoroacetic acid followed by diazotiz-ation gives the acyl azide (202) which, in thermolysis in benzene and subsequent interception of the resulting isocyanate with r-butanol, yields the protected 3-amino-/3-lactam (203) (73JCS(P1)2907). [Pg.265]

Alternative routes to -amino acids have also been explored and involve, stereoselective alkylation of chiral derivatives of y9-alanine [136-140], Curtius rearrangement of enantiomerically pure and regioselectively protected substituted-succinic acids [134, 141, 142] (the approach is also suitable for the synthesis of y9 -amino acids [143]), or the formation of chiral isoxazolidinone intermediates [144]. [Pg.48]

This version of the Curtius rearrangement has been applied to the synthesis of amino acid analogs and structures containing amino acids. Several m-2-aminocyclopropane carboxylate esters were prepared by selective hydrolysis of cyclopropane-1,2-dicarboxylates, followed by reaction with DPPA.267... [Pg.948]

An attempted synthesis of biotin using thiocarbonyl ylide cycloaddition was carried out (131,133,134). The crucial step involves the formation of the tetrahydrothiophene ring by [3 + 2] cycloaddition of a properly substituted thiocarbonyl ylide with a maleic or fumaric acid derivative (Scheme 5.27). As precursors of the thiocarbonyl ylides, compounds 25a, 72, and 73 were used. Further conversion of cycloadducts 74 into biotin (75) required several additional steps including a Curtius rearrangement to replace the carboxylic groups at C(3) and C(4) by amino moieties. [Pg.332]

The pyrido[3,2-rflpyrimidines 370 were prepared from 2,3-pyridinedicarboxylic acid anhydride 366 by the action of boiling MeOH to give the stable isomer of half-ester 367. Subsequent treatment with ethyl chloroformate in presence of EtsN and NaNs formed the azide 368 that was transformed by Curtius rearrangement into the isocyanate 369. Reaction of 369 with a series of amino acids under mild conditions gave adducts 370 (Scheme 12) <2003TL2745>. [Pg.799]

Curtius rearrangement of the heteroaroyl azides, obtained from the reaction of the carboxylic acid chlorides with sodium azide, provides a route to the amino-pyrroles and -indoles (e.g. B-70MI30504, B-77MI30506, 78CPB1054), which, because of the ease of synthesis of the carboxylic acids, is frequently preferable to reduction of the nitro compounds. [Pg.288]

The Curtius rearrangement provides a route to carbamates of a-amino sulfonamides (Scheme 25). 108 Reaction of the ethyl ester of an a-bromo acid 52 with Na2S03 yielded the sodium salt of the corresponding sulfonic acid 53. Treatment of 53 with PQ5 afforded the sulfonyl chloride 54 which on reaction with an amine gave the sulfonamide 55. The latter... [Pg.479]

Goodman and Chorev 75 found that the required a-aminoacyl azides 14 are best prepared by reaction of the mixed anhydride of the amino acid with sodium azide. This method led to slightly better yields than the nitrosylation of TV-formylaminoacyl hydrazide. Curtius rearrangement of the a-aminoacyl azide 14 yielded the isocyanate 16, which was subsequently trapped as 17 or 18 as shown in Scheme 2. Comparable yields were obtained by nitrosylation with tert-butyl nitrite. 76 Other methods of acyl azide formation have rarely been employed for PMRI-peptide synthesis. Only Fincham et al. 11 reported the use of trimethylsilyl azide to synthesize an acyl azide en route to a PMRI-peptide. [Pg.535]

The first step in the overall synthetic scheme (Scheme 6) is the condensation of an appropriate carboxylic acid with trifluoroacetaldehyde. The carboxylic acid is chosen to impart specificity for the target enzyme. In one example,[28 the dianion of cyclohexanepropanoic acid (29) was formed by the addition of LDA and then quickly condensed with trifluoroacetaldehyde to form the p-hydroxy acid 30 as a racemic mixture of erythro- and threo-isomers. The p-hydroxy acid 30 is then protected with TBDMSOTf forming 31. Diphenyl phosphorazidate, TEA, and benzyl alcohol were then utilized in a Curtius rearrangement of the protected alcohol 31, which proceeds through an isocyanate intermediate that yields the protected amino alcohol 32 upon reaction with benzyl alcohol. In order for this step to occur at an appreciable rate, a second equivalent of triethylamine had to be added. The amino alcohol 32 was then deprotected and coupled with Boc-Phe-Leu-OH to give the trifluoromethyl alcohol 33, which was oxidized to the corresponding trifluoromethyl ketone 34 as a 1 1.2 mixture of diastereomers using the Dess-Martin periodinane procedure. Thus far, the compound shown in Scheme 6 is the only compound that has been synthesized by this method, but it is reasonable to assume that many other similar fluoro ketones can be produced by this scheme. [Pg.239]

Pyridopyrimidine systems may also be accessed by in situ generation of pyridylisocyanates <2003TL2745>. Treatment of 2,3-pyridinccarboxylic anhydride with methanol leads to the formation of 2-(methoxycarbonyl)nicotinic acid that undergoes Curtius rearrangement on conversion to the 3-acyl azide with sodium azide and ethyl chloro-formate. Condensation of the resulting isocyanate with a series of amino acids leads to the synthesis of pyrido[3,2- T pyrimidines in good to excellent yield (Scheme 19). [Pg.130]

Forosamine is an amino sugar component of the antibiotic Lepicidin. Since Le-picidin is sensitive to acid and catalytic hydrogenation, an Fmoc group was selected to protect the amino function. A rather unconventional method was used to introduce it [Scheme 8.94].230 A Curtius rearrangement on the acyl azide derived from carboxylic acid 94.1 proceeded with retention of configuration to give the isocyanate intermediate 94.2 that was trapped with 9-fluorenylmethanol to afford the N-Fmoc derivative 94J in 72% yield. [Pg.481]

The two functional groups of (6g) could also be transformed i,e the acid chloride into the isocyanate (6j) (84 %) via a Curtius rearrangement and then into the carbamate (6k) (78%) which oxidation led to the amino alcohol (61) (65 %). All these transformations are stereoselective (Figure 5). [Pg.467]

Acyl azides are easily handled by acetic acid-catalysed Curtius rearrangement which generates one mole of nitrogen per azide This can be done conveniently on a micro scale with no interference from such groups as nitro, nitroso, azoxy, azo, hydrazo, cyano, amido, imido, amino or ammonium. Diazo or A -nitroso groups do interfere. [Pg.194]


See other pages where Curtius rearrangement amino acids is mentioned: [Pg.138]    [Pg.48]    [Pg.776]    [Pg.101]    [Pg.579]    [Pg.106]    [Pg.362]    [Pg.878]    [Pg.1001]    [Pg.8]    [Pg.319]    [Pg.182]    [Pg.226]    [Pg.534]    [Pg.535]    [Pg.536]    [Pg.537]    [Pg.799]    [Pg.571]    [Pg.571]    [Pg.276]    [Pg.747]    [Pg.411]    [Pg.755]    [Pg.575]    [Pg.986]    [Pg.363]    [Pg.358]    [Pg.373]    [Pg.635]    [Pg.418]    [Pg.571]    [Pg.635]    [Pg.704]   
See also in sourсe #XX -- [ Pg.144 ]




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