Other Guanidines

Nine 2-amino imidazole alkaloids were isolated from a Red Sea calcareous sponge, Leucetta chagosensis (50,51). They belong to four differ- 

Grossularins I (37) and II (38), the first examples of naturally occurring a-carbolines, were obtained from a French solitary tunicate (Dendrodoa grossularia) and were found to be cytotoxic toward L1210 leukemia cells (55). Previously the structure of grossularin I was proposed as 39 (56), which was revised to 37 on the basis of comparison with the structure of grossularin II (38). Structural proof for 38 was unambiguously provided by X-ray analysis. The same tunicate contained 3-indolyl-4//-imidazol-4-one (40), the structure of which was confirmed by synthesis (57). The imidazo-lone compound (40) was devoid of cytotoxicity. 

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Furthermore, the same sol-gel matrices have been used in a system where acid and base catalysis occur in the same pot without quenching either catalyst [29]. In this case, the acids were either entrapped Nafion (perfluorinated resin sulfonic super acid, a3) or entrapped molybdic acid (M03-Si02, a2), while the bases were two ORMOSILs (organically modified silica sol-gel materials), one with H2N (CH2)2NH(CH2)3 groups (bi) and the other guanidine base residues (b2) (Scheme 5.12). 

As found with guanethidine, doses of other guanidines sufficient to cause marked depletiort of noradrenaline from tissues such as heart or spleen, fail to lower the catecholamine content of the brain or adrenals. This has been shown for j3-hydroxyphenethylguanidine (LXXXVll) [265], guanisoquin (LXVII, R = 7-Br, = H) [277], 3-phenoxypropylguanidine (LXXXV) [249],... 

At a concentration of 6-3 mM, guanethidine had no effect on catechol-0-methyltransferase [440]. No other guanidines appear to have been tested against this enzyme. In contrast, the inhibition by guanidines of monoamine oxidase, the other important enzyme involved in noradrenaline destruction, has been... 

Mme Teindas, MP 31, 55-57 (1949) (Analytical methods applicable to manuf of cyanoguanidine other guanidine derivs ) 16)Kirk Othmer 4 (1949), 673 17)cy wSSiid s Nitrogsn Chemical Digest, The Chemistry of Dicyandiamide , American Cyanamid Co, NY, Vo 3 (1949) 18)1-. 

Rather puzzling was the low pKa (<8) value of dibromophakellin (137) compared to other guanidine derivatives. The X-ray analysis, however, demonstrated that the aminoimidazole ring is somewhat twisted and cannot become planar on protonation. The mesomerism within the cation must therefore be considerably reduced. 

Stmwe, Ber 55, 457(1922) CA 16, 2482(1922) (Preparation of Guanidine Chlorate and other guanidine salts) 5) Cyanatnid s Nitrogen Chemicals Digest, Vol IV, NV (1950)... 

Shiga. TJebet einige Hefefermente, Zeits. f. physiol. Chem., 1904, (42), p. 303. Daeim. The action of arginase upon Creatin and other Guanidin derivatives, Jmm. of Biol. Chem., 1907, (3), p. 435. 

Other guanidine accelerators may substitute for DPG, but they also have toxicity issues. They will also impart different cured physical properties that must be evaluated. The strong toxicity concerns with the use of DPG are driving an effort to find new substitutes for it. 

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