Thioureas biological activities

Platinum-thiourea complexes have been extensively studied because of their biological activity [54], but few have been used in catalysis. Neutral thioureas are able to coordinate to metal centres through their sulfur atom (Scheme 9) [55,56] monomeric (I) and oligomeric (II) species are known for Rh [57], and an X-ray structure has also been determined for the chiral complex III [58]. In many complexes hydrogen bonding has been observed... 

Substituted thioureas have been extensively studied over the decades. Reaction of CoX2 (X = C1, Br) with substituted phenylthioureas yield a range of complexes involving halide and thiourea as ligands, characterized by spectroscopy and thermogravimetric analysis.503 Both [Co(Rtu)4(OH2)2]2+ (Rtu = thiourea, phenylthiourea, allylthiourea) and [Co(Rtu)2(OH2)4]2+ (Rtu = diphenylthiourea) have been prepared and characterized as low-spin octahedral species.504 The octahedral bis(phenylthiourea)bis(dithiolate)cobalt(II) complex, one of a number of complexes of phenylthiourea, chlorophenylthiourea and bis(diphenylphospinothioyl)methane prepared and characterized,505 proved the most biologically active of those tested. 

In his approach toward selenium-containing heterocycles with potential biological activity, Abdel-Hafez reacted 2-amino-3-(4,5-dihydro-17/-imidazol-2-yl)-4,5,6,7-tetrahydro-l-benzoselenophene 297 with triethyl orthoformate and benzaldehyde to generate the tricyclic systems 296 and 298, respectively (Scheme 21) <2005RJ0396>. Similarly, reaction with carbon disulfide gave the corresponding thiourea 299. 

The Pictet-Spengler reaction is the method of choice for the preparation of tetrahydro-P-carbolines, which represent structural elements of several natural products such as biologically active alkaloids. It proceeds via a condensation of a carbonyl compound with a tryptamine followed by a Friedel-Crafts-type cyclization. In 2004, Jacobsen et al. reported the first catalytic asymmetric variant [25]. This acyl-Pictet-Spengler reaction involves an N-acyliminium ion as intermediate and is promoted by a chiral thiourea (general Brpnsted acid catalysis). 

The latter approach has been exemplified in a number of published cases. An indication of the development requirements of well-known reactions for successful employment in array synthesis is provided by the work ofWatson and co-workers [15] to prepare thiazole derivatives. Adaptation of the Hantzch synthesis of 2-aminothiazoles (Fig. 2) from a-haloketones and thioureas was used in the one-step preparation of discrete samples. Inclusion in the array of a compound of known biological activity provided a valuable internal control. 

Carbodiimides can be used as stabilizers in thiophosphate based pesticides to prevent hydrolytic degradation. Some carbodiimides show insecticidal and acaricidal properties. Diafenthiuron [l-t-butyl-3-(2,6-diisopropyl-4-phenoxyphenyl)thiourea], an effective insecticide and acaricide, may act via its derived carbodiimide. This transformation is accomplished by sunlight degradation in aqueous solution. The carbodiimide causes inhibition of ATP phosphorylation. An H-labeled derivative of diafenthiuron, [phenoxy-4- H]diafenthiuron, has been prepared to study its photochemical and metabolic degradation. " The biological activity of N-(pyrid-3-yl)thioureas toward spider mites is sensitive to the kinetics of the formation of the carbodiimides and their photochemical stability. ... 

The natural fatty acid amides are mixtures of saturated fatty acid amides and unsaturated fatty acid amides. The present invention is based on the fact that the unsaturated fatty acid amides can be isolated very easily from a mixture of fatty acid amides by treating the fatty acid amides with urea or thiourea. The unsaturated fatty acid amides have more effective biological activity. 

On the other hand, isothiocyanates are known to be reactive with a variety of food constituents, such as amines, amino acids, proteins, thiols, and alcohols, due to their electrophilic properties to give a variety of compounds, including thioureas and dithiocarbamates [32]. Despite their chemical nature, only limited information has been made available regarding the stability of isothiocyanates and the biological activity of reaction products of isothiocyanates with food constituents [33-35]. 

Many biologically active compounds contain cyclic ureas, including inhibitors of human immunodeficiency virus (HIV) protease and HIV replication [70]. Kim et al. [71] presented an illustration of the synthesis of oligomeric cyclic ureas as nonnatural biopolymers. Applying the libraries from libraries [72] concept, triamines [65] such as those described earlier were used as templates for the generation of different heterocyclic compounds such as cyclic ureas, cyclic thioureas, and bicyclic guanidines [65]. The cyclizations to obtain the five-membered ring cyclic ureas and cyclic thioureas were... 

The thiazole ring system is a useful structural motif found in numerous biologically active molecules. Addition of thioamide or thiourea to the aqueous solution of phenacyl bromide-j3-CD complex gave the corresponding thiazole or aminothiazole, respectively (>82%), without the formation of by-products or rearranged products (Figure 4.16). The role of CD appears to be to activate and solubilize the phenacyl bromide, and drive the reaction to completion in decreased reaction times. Without CD, the reaction took place but the yields were poor (20%). Selenazoles were also prepared from a-bromoketones and selenourea in the presence of )3-CD at 50 °C under atmospheric pressure. ... 

Since oxazolidines and oxazolidinones are fiindamental structural classes in organic chemistry (chiral auxiliaries) and in medicinal chemistry (e.g., Linezolid) and since they mask P-hydroxy-a-amino acids, which are widespread in various biologically active compounds and in natural products, the enantioselective synthesis of oxazolidinones is a challenging topic. Indeed, a new method for the direct synthesis of chiral 4-carboxyl oxazolidinones 168 by the catalytic asymmetric aldol reaction of isocyanato-malonate diesters 166 with aldehydes 167 in the presence of a thiourea catalyst (TUC) was developed. Since the resulting chiral 4-carboxy oxazolidinones are the equivalent of P-hydroxy-a-amino acids, this procedure... 

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