Biological activity mercapto

Purine, 6-iodo-alkylation, 5, 530 synthesis, 5, 563, 597 Purine, 6-iodo-9- -D-(2,3,5-tri-0-acetyl)ribofuranosyl-synthesis, 5, 598 Purine, 9-isopropyl-deuterium-hydrogen exchange, 5, 527 Purine, 9-(2,3-0-isopropylidene-/3-D-ribofuranosyl)-6-methoxy-synthesis, 5, 584 Purine, 6-mercapto-biological activity, 5, 604 metabolism, 1, 237 as pharmaceutical, 1, 159 tautomerism, 5, 509 Purine, 2-methoxy-synthesis, 5, 596 Purine, 6-methoxy-irradiation, 5, 543 riboside... 

Solid-phase library synthesis of triazolopyridazines via a [4+2] cycloaddition strategy has been accomplished <99TL619>. Intramolecular bis-Mannich reaction of 3-aryl-5-mercapto-13,4-triazole, formaldehyde and a-phenylethylamine yields chiral 5-aryltriazolo[3,4-ft]-[133]thiadiazine derivatives. These compounds have been screened for antibacterial activities and some of them show potent biological activity <99SC2027>. 

Gebelein and coworkers have prepared monomers and polymers based on the antineoplastic agents 5-fluorouracil and 6-mercapto-purine (26). These polymers would be potentially useful in treating various types of cancer or leukemia and some derivatives have shown biological activity. Previous work by this group has Included the synthesis of polyisoprene derivatives containing sulfa drug, carbamate, urea, oxazolldone and oxazole units (27.28). 

Mercapto-6-substituted androstenediones have also been described in a recent Farmitalia patent [178], although no details are available on the biological activity. 

Thiazolidones are another class of heterocycles that attract much attention because of their wide ranging biological activity [106], They are usually synthesized by three-component condensation of a primary amine, an aldehyde, and mercapto-acetic acid with removal, by azeotropic distillation, of the water formed [107]. The reaction is believed to proceed via imine formation then attack of sulfur on the imine carbon. Finally, an intramolecular cyclization with concomitant elimination of water occurs, generating the desired product. The general applicability of the reaction is limited, however, because it requires prolonged heating with continuous removal of water. To circumvent these difficulties and to speed up the synthesis, Miller et al. developed a microwave-accelerated three-component reaction for the synthesis of 4-thiazolidinones 63 [108]. In this one-pot procedure, a primary amine, an aldehyde, and mercaptoacetic acid were condensed in ethanol under MW conditions for 30 min at 120 °C (Scheme 17.44). The desired 4-thiazolidinones 63 were obtained in 55-91% yield. 

Further, 1,2,4-triazinones, 1,2,4-triazine thiones, and their numerous derivatives are of interest for the synthesis of biologically active compounds. For instance, 4-amino-6-arylmethyl-3-mercapto-l,2,4-triazin-5(4//)-ones were condensed with suitably substituted 5-aryl-2-furfurals or 5-aryl-2-furoic acids to obtain biologically active derivatives 201 and 202 which exhibit antibacterial activities compared to furacin (Figure 11) <2003IJH85>. 

Biological activities— The 5-halo derivatives and the mercapto analogues of cytosine have been discussed in Part I of this review. Cytosines with fraudulent sugars have received extensive study. Although a discussion of this type of modification is beyond the scope of this review, the fact that cytosine arabinoside [285, 286] (LVI, l-/S-D-arabinofuranosylcytosine, Ara-C, CA, cytarbine) is a potent antiviral agent against herpes and vaccinia virus [287-293] as well as a potent antileukaemia agent must not escape mention. In the latter case cytosine arabinoside is not only effective in transplantable... 

Chiral tetrahydrothiophenes are compounds displaying important biological activities. They were obtained also through an enantioselective domino sulfa-Michael-Michael process of a,(3-unsaturated aldehydes with ethyl 4-mercapto-2-butenoate [47]. While catalyst 17a turned out to be ineffective, the diarylprolinol silyl ether 17b afforded cyclic products with high to excellent enantio- and diastereoselectivity (Scheme 14.16a). A closely related sulfa-Michael aldol process was developed by using 3-mercapto a-carbonyl esters as reaction partners. The best stereoselectivity and yield were obtained with diaryl prolinol 17c in the presence of small amounts of H2O (Scheme 14.16b) [48]. 

An example of application of this reaction employing NH OAc as a source of ammonia is depicted in Scheme 12.3. It is a key step in the preparation of a pyrimidine-imidazole-based library, where their biological activities were under study [7-9]. Thus, using glyoxal dimethyl acetal 11, ammonium acetate, and the required asymmetrical 1,2-diketone 10, prepared from 4-fluorobenzoate 9 and 2-mercapto-4-methylpyrimidine 8, the key intermediate 12 was obtained in good yield (86%). 

A number of different chemical forms of lipoic acid are known to occur. Those with biological activity are the disulfide, dimercapto, mono-5-acyl, and the mono-mercapto forms. ... 

Amino-2-arylazo-2-butenoic acids (289) have been prepared by two pathways from acetoacetic esters. The reaction of these compounds with bligomeric a-mercapto-aldehydes leads to substituted thiazoleacetic esters (290), which appear to be useful intermediates for the synthesis of penicillin analogues. Most syntheses of 2,4-dioxa-l,3-thiazolidines (292), which show an interesting spectrum of biological activity, involve oxidation of thiol precursors. A new method uses readily available dihydropyrimidine thiones in reaction with chloro-acetic acid. The reaction does not proceed if R = H in (291). 

So far as is known, mercapto- or haloquercitols do not occur in Nature. It seems probable that some of these cyclitols will show inositol activity or anti-inositol activity in biological systems. However, tests of four haloquercitols with human, cancer-cell cultures gave negative results. ... 

Michael s original (non-biological) donors were carbanions derived from an activated methylene-group as in diethyl malonate, but the most likely Michael donors in enzymes are the anions of either the NH— group in imidazole (as in Bloch s original discovery), or the hydroxy-group of serine, or the mercapto-group of cysteine. 

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