Guanidine class

DPG is the most commonly used member of the guanidine class of rubber accelerators. DPG is commonly used as a secondary accelerator (or kicker ) with primary sulfenamide accelerators and sometimes with thiazole accelerators as well. DPG is also a silanization accelerator. It can interact with the silica surface, which then reacts with organosilanes in tread stocks to help reduce rolling resistance. DPG is not as chemically active as the thiuram or dithiocarbamate accelerators. 

It is common practice in the mbber industry for a compounder to use combinations of several accelerators in developing a cure system. Typically these cure systems are comprised of a primary accelerator and one or more secondary types. Primary accelerators are generally the thiazole and sulfenamide classes the secondary types (kickers) are the thiurams, dithiocarbamates, guanidines, and to a much lesser extent, certain amines and the dialkylphosphorodithioates (20). 

Accelerators are chemical compounds that iacrease the rate of cure and improve the physical properties of the compound. As a class, they are as important as the vulcanising agent itself. Without the accelerator, curing requires hours or even days to achieve acceptable levels. Aldehyde amines, thiocarbamates, thiuram sulfides, guanidines, and thiasoles are aU. classified as accelerators. By far, the most widely used are the thiasoles, represented by mercaptobensothiasole (MBT) and bensothiasyl disulfide (MBTS). 

Interposition of a methylene group between the phenyl ring and the heterocycle leads to the benzyldiami nopyrimidines, a class of compounds notable for their antibacterial activity. Condensation of hydrocinnamate 54 with ethyl formate leads to the hydroxymethylene derivative 55. In this case, too, the heterocyclic ring is formed by reaction with guanidine. This sequence probably involves initial addition-elimination to the forniyl carbon to form 56 cyclization in this case involves simple amide formation. Tautomerization then affords the hydroxy derivative 57. This is converted to tetroxoprim (58) by first... 

A class of drug derived from guanidine, including metformin and phenformin. Metformin is currently widely used in humans for the treatment of type 2 diabetes. Phenformin was formerly also widely used but was withdrawn because of problems with lactic acidosis. 

Hexanitrodiphenylguanidine. Note guanidines are included here, although A.F. McKay et al (Ref 4) states .. . these compds should not be classed as nitrimines ... 

Marine sponges are a source of an array of polycyclic diamine alkaloids of common biogenetic origin. This class of secondary metabolites has been the subject of four previous reviews [4-7]. Therefore, the present review will include literature reports previously not discussed, dealing with the isolation, structure determination, biological activities, and total synthesis of polycycUc diamine alkaloids isolated from marine sponges. This review will not include guanidine alkaloids [8,9] or the manzamine alkaloids [10,11], since these compounds have been recently reviewed elsewhere. Only polycycUc... 

For the purpose of polymer/additive analysis most applications refer to vulcanisate analysis. Weber [370] has determined various vulcanisation accelerators (Vulkazit Thiuram/Pextra N/Merkapto/AZ/DM) in rubbers using PC. Similarly, Zijp [371] has described application of PC for identification of various vulcanisation accelerator classes (guanidines, dithiocarbaminates, thiuramsulfides, mercapto-substituted heterocyclic compounds, thioureas, etc.). The same author has also... 

The structures of drugs that have proven clinically useful for treatment of hypertension tend to fall into discrete classes according to their mode of action. It is thus usually a safe assumption that a drug containing a guanidine function will show the... 

Various guanidines linked by an alkylene chain to heteroaromatic rings have shown activity at adrenergic nerve endings the reported activities of compounds in this class are listed in Table 3.20. These include the thenylguanidine (LX)... 

Resonance stabilization of the conjugate acid of guanidine defines this class of molecules as some of the strongest bases in organocatalysis [114],... 

Ishikawa and co-workers also reported a class of structurally modified guanidines for promotion of the asymmetric Michael reaction of ierf-butyl-diphenylimino-acetate to ethyl acrylate [124,125]. In addition to a polymer support design (Scheme 69), an optical resolution was developed to achieve chiral 1,2-substituted ethylene-l,2-di-amines, a new chiral framework for guanidine catalysis. The authors discovered that incorporating steric bulk and aryl substituents in the catalyst did improve stereoselec-tivitity, although the reactivity did suffer (Scheme 70, Table 4). 

Most solid-phase strategies for the preparation and protection of guanidines were developed to enable the use of arginine in solid-phase peptide synthesis. In recent years, however, the biological activity of many guanidines has spurred a quest for more versatile solid-phase syntheses of this class of compound. 

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