Amino acids thiophosgene

Pteridine synthesis from pyrazine precursors are usually applied in such cases where the formation of special derivatives cannot be achieved easily by the pyrimidine approach. Methyl 3-amino-2-pyrazinecarboxylate (362) reacts with thiophosgene to give the corresponding 3-isothiocyanato derivative (363) which cyclizes with primary amines, arylalkylamines, aminoalcohols, amino acids,... 

Metal chelating amino acid derivatives of cellulose were recently obtained via modification of cellulose with 2,4-toluenediisocyanate, followed by treatment with amino acid ester derivatives [58,59]. Diisocyanates are able to crosslink cellulose chains and/or to yield reactive cellulose isocyanate, depending on the reaction conditions. Sato and his coworkers [60] examined the optimum conditions for the reaction between cellulose and 2,4-toluenediisocyanate and succeeded in introducing 0.30 mol of free isocyanate group per glucose unit. Cellulose isocyanate was further converted into isothiocyanate [61]. This derivative has also been synthesized by condensation of cellulose with 2,4-diisocyanototoluene, followed by hydrolysis and thiophosgene treatment [61]. 

So far, we have considered protocols that result in chiral centres in the C and position (actnally always with the same substiment). Let us now turn to satnrated carbenes that have only one chiral centre in the backbone. Figure 5.15 shows a procedure that utilises a chiral diamine derived from proline, a naturally occurring a-amino acid. Reaction with aniline to the corresponding amide and reduction with LiAlH yields the diamine used [60]. The actual synthesis of the chiral carbene then calls for reaction of the proUne derived diamine with thiophosgene and subsequent S/Cl exchange with oxalyl chloride [50]. The... 

Ethyl 3-isothiocyanatopyridine-2-carboxylate (6) is available from the corresponding amino compound and thiophosgene in water/dichloromethane as a two-phase system.428 It is converted into 3-amino-2-sull anylpyrido[3,2-< /]pyrimidin-4(37/)-one (7, R = NH2) directly with hydrazine and into 3-substituted 2-sulfanylpyrido[3,2-c/]pyrimidin-4(3//)-ones with various primary amines, amino alcohols,428 and amino acids.429... 

Thiophosgene is also able to react with amino acids, with the formation of thiourea, and can even react simultaneously with thiol and amino groups. Thus, for example, with cysteine (3), 2-thiazolidinethion-4-carboxyIic acid (4) is formed (Lukens and Sisler, 1958a) ... 

Similarly, thiohydantoins 29 were prepared by using thiophosgene or thiocarbonyldiimidazole as the reagent. A combinatorial library containing 6364 individual thiohydantoins was then assembled in the positional scanning format. For this library, 74 and 86 amino acids were used in the Rj and R3 positions, respectively. 

Treatment of 3-amino-6-methoxypyridine or the corresponding thiourea 471 with thiophosgene gives the l,3-thiazetidine-2-thione 472. 1,3-Thiazetidine-2-thiones are possible intermediates in the reaction of carbon disulfide or isothiocyanates with isothioureas,in the reaction of carbon disulfide with imines, " and in the reaction of salts of dithiocarbamic acids with a,/3-unsaturated acid chlorides. 4-Imino-l,3-thiazetidine-2-thione is suggested as an intermediate in reactions of isothiocyanic acid (HNCS). ... 

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-... 

A number of esters derived from 2-isothiocyano-3-thiophencarboxylic acid (134) has been prepared from the corresponding amino derivatives, prepared by the Gewald reaction, through the reaction with thiophosgene and sodium bicarbonate in a water-chloroform mixture. Similarly, 2-carboethoxy-3-isothiocyanothiophen wps prepared from... 

---