Guanidine, benzyl

Gramine methiodide, reaction with p3nri-dinium salts, 97 Guanidine, benzyl-, 281 Guanine, 7- and 9-alkyl-, quatemization of, 44... 

In certain cases, free guanidines can also serve as precursors to Group 4 metal guanidinate complexes. The bis(guanidinato) bis(benzyl)zirconium complex [Pr NHC(NPr )2]2Zr(CH2Ph)2 was obtained by addition of 2 equivalents of... 

Tautomerism. Owing to the presence of the guanidine moiety in the structure of tegaserod, the three tautomers shown below are possible. Tautomer 6a is assigned to the solid state of tegaserod, as confirmed by X-ray structure analysis of the 5-0-benzyl derivative. In solution, 6b and 6c also exist in equilibrium depending on the experimental conditions. For instance in DMSO, the solvent used to measure NMR spectra, 6b is preferred. Tautomer 6c is formed in methanol after exposure to xenon light, and from this solution the tautomer can even be separated by HPLC. 

Some substituted guanidines have been obtained [457] by reaction of amines with the disulphide H2N(HN )C S S C( NH)NH2. Papers on the structure and p/fa s [458], and the synthesis [458, 459] of acylguanidines have been published. Reaction of guanidine with alkyl-, alkenyl-, and benzyl-halides, followed by distillation under basic conditions, is reported to give useful yields of amines [460]. A novel electrophilic substitution of benzene to give A -methyl-A -phenyl-guanidine amongst other products has been published [461 ]. 

S-benzyl-zso-thiuronium chlorides 164 with sulfur monochloiide provides a convenient method for preparing S-benzyl-l,2,3,5-dithiadiazolium chlorides 165 (2002ARK224). Based on the formation of similar products from amidines and guanidines with sulfur dichloride, the authors proposed a mechanism which included the addition of two S2CI2 molecules to amidine 164 followed by HCI and sulfur extrusion (Scheme 86). 

The reaction of arylisothiocyanates with guanidines (233) affords amidinothioureas (234), which can be converted into 3,5-diarylimino-l,2,4-thiadiazolines (235) directly on treatment with bromine in ethanol. Alternatively, (234) can be alkylated with benzyl chloride to give the S-benzyl derivative (236) which on treatment with bromine in chloroform gives (235) (Scheme 51) <87JIC675>. 

The reaction works well when R and are alkyl or benzyl, or when NR R is a cyclic secondary amine. ° It also works with benzil and its para-substituted derivatives and with guanidine and its mono-substituted derivatives, giving high yields of products 35 having Ar = phenyl para-substituted with H, Cl, Me, and MeO, and R = R = R = H,... 

Analogerhalt man aus (Benzylidenamino)-guanidin die entsprechenden 4-Aryl-2-(2-benzyl-iden-hydrazino)- bzw. 2-(2-Benzyliden-hydrazino)-4,5-diary 1-imidazole107,108 ... 

NH XT sAnH2 HCOONH Pd —C/CH3OH (trocken) 20-25° 25 min N- (4-Amino-benzyl) -guanidin 70 5... 

Coupling of a benzyl bromide and a resin-bound stannane in the presence of a protected guanidine (Scheme 51), en route to solid-phase synthesis of bradykinin antagonists, is also reported in this patent.101... 

Several strategies enable the attachment of guanidines and amidines to insoluble supports (Figure 3.29, Table 3.28). These include attachment as A-benzyl, A-acyl, and A-alkoxycarbonyl derivatives. Furthermore, support-bound isothioureas can be used to convert amines into guanidines. The synthesis of support-bound guandines is considered in Section 14.3. 

Chemical Name Guanidine, l-benzyl-2,3-dimethyl-, sulfate (2 1)... 

Corey and Grogan recently developed a novel catalytic enantioselective Strecker reaction which utilized the readily available chiral C2-symmetric guanidine 19 as a bifunc-tional catalyst [12], The addition of hydrogen cyanide to achiral aromatic and aliphatic N-benzhydrylimines 18 gave N-benzhydryl-a-aminonitriles 20 (Scheme 7), which were readily converted to the corresponding amino acids with 6 N HCI. The use of N-benzyl- or N-fluorenylimines afforded products of poor enantiomeric purity. 

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