Thiocarbonyl compounds amino acids

This chapter covers the recent advances in amidocarbonylations, cyclohydrocarbonylations, aminocarbonylations, cascade carbonylative cyclizations, carbonylative ring-expansion reactions, thiocarbonylations, and related reactions from 1993 to early 2005. In addition, technical development in carbonylation processes with the use of microwave irradiation as well as new reaction media such as supercritical carbon dioxide and ionic liquids are also discussed. These carbonylation reactions provide efficient and powerful methods for the syntheses of a variety of carbonyl compounds, amino acids, heterocycles, and carbocycles. 

The lithium derivatives described above react with electrophiles such as alkyl halides, carbonyl compounds, and thiocarbonyl compounds, resulting in the corresponding 3-substituted derivatives (190). Hydrolysis of these products by dilute acid as described in Section B,1 gives the new nonproteinogenic amino acid ester (191) along with the original amino acid ester used as the chiral auxiliary. The chemical yields are above 80% (83MI1). 

Support-bound 1,2-diamines can be readily converted into imidazolidinones by treatment with carbonyl diimidazole [128,129]. The required diamines have been prepared on cross-linked polystyrene by reduction of peptides bound to MBHA resin with borane. Similarly, bicyclic imidazolines have been prepared from triamines and thiocarbonyl diimidazole (Entry 10, Table 14.3). Dehydration of polystyrene-bound monoacyl ethylene-1,2-diamines yields 4,5-dihydroimidazoles (cyclic amidines, Entry 5, Table 13.18). Several groups have reported the synthesis of 2-aminoimidazol-4-ones from resin-bound amino acid derivatives (e.g., Entry 6, Table 15.11). Most of these compounds are, however, unstable, and slowly decompose if dissolved in DMSO (Jesper Lau, private communication). 

It has been shown also that both thiocarbamoylimidazoles 147 and 148 can react with sodium azide. These compounds were successfully used to prepare heterocycle-peptide conjugates as peptidomimetics. A-Terminal aminothiatriazole modified amino acids have been synthesized using two methods (Scheme 35). To prepare monosubstituted aminothiatriazoles 151 the amino acid derivatives were converted into the thiocarbamoyl imidazoles of type 147 that can react with azide ion to form the thiatriazole ring. On the other hand, for the synthesis of disubstituted amino acid derivatives of 1,2,3,4-thiatriazoles 153 and 155 the activation of the thiocarbonyl group via a salt of type 148 was required. The reaction conditions and the yields of thiatriazoles 151, 153, and 154 prepared by this approach are shown in Scheme 35. 

Reactions.—Recent investigations concerning the reactivity of seleno-carbonyl compounds have dealt exclusively with reactions analogous with well-known reactions of thiocarbonyl compounds. Thus, 6-chloropurine 3-oxide has been converted into l,6-dihydropurine-6-selenone 3-oxide by means of selenourea, a series of 2-amino-l,3,4-selenadiazoles have been prepared by the reaction of selenosemicarbazide with carboxylic acids or... 

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. 

Treatment of thionhydrazides, RC(==S)—NH—NH2 with nitrous acid should lead to thiocarbonyl azides, RC(=S)—N3, and it seems likely that these azides are indeed formed as short-lived intermediates. The isolated products are 1,2,3,4-thiatriazoles. When thiosemi-carbazides are nitrosated, 5-amino-l,2,3,4-thiatriazoles or/and 5-mercaptotetrazoles are obtained. Freundformulated his products as such in 1895, while Oliveri-Mandala considered them thiocarbamoyl azides on the basis of some chemical evidence. Lieber resolved this controversy by recording the infrared spectra of the compounds and demonstrating the absence of an azide band . He did the same for the 5-alkylmercapto-l,2,3,4-thiatriazoles , which had earlier been reported as azido-dithiocarbonates , and for the products from azide ion and thiophosgene and carbon disulphide , all of which possess thiatriazole structures. Lieber also demon-... 

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