Dopastin

The thermal degradation over temperature and time of selected amino acids (Asp, Gln, and Glu) in the presence of reducing sugars was investigated in low moisture model systems. Copyrolysis of glucose-Asp mixtures led to the release of acrylic acid, attaining >5 mmol/mol Asp at 230 degrees C after 5 min. Spurious amounts of 3-butenamide were detected upon heating Gln together with a carbonyl source. Apparently, intramolecular cyclization is favored to procure 2-pyrrolidinone, reaching levels >3 mmol/mol above 230 degrees C. 2-Pyrrolidinone was also formed in comparable amounts in pyrolyzed sugar-Glu mixtures, indicating that the Maillard reaction may be an important contributor to the formation of 2-pyrrolidinone in certain cooked foods. The chemical route to acrylic acid and 3-butenamide is probably analogous to that described for acrylamide recently. Evidence is also presented that acrylic acid may be an intermediate in the formation of acrylamide, and yields could be augmented by coincubation of fructose-Asp with certain amino acids such as Gln, reaching approximately 5% of the yield obtained by the Asn route.

The regiospecific [2 + 2] cycloaddition of cyclic isoimidium salts with ynamides is described. This effort led to the development of the first successful example of a catalyst-free, thermally driven Ficini [2 + 2] cycloaddition process of ynamides with α,β-unsaturated carbonyl compounds, giving the stable cyclobutenamides in excellent yields (up to 99%).

Metanephric organ culture has been used to determine whether embryonic kidney tubules can be stimulated by cAMP to form cysts. Under basal culture conditions, wild-type kidneys from embryonic day 13.5 to 15.5 mice grow in size and continue ureteric bud branching and tubule formation over a 4- to 5-d period. Treatment of these kidneys with 8-Br-cAMP or the cAMP agonist forskolin induced the formation of dilated tubules within 1 h, which enlarged over several days and resulted in dramatically expanded cyst-like structures of proximal tubule and collecting duct origin. Tubule dilation was reversible upon withdrawal of 8-Br-cAMP and was inhibited by the cAMP-dependent protein kinase inhibitor H89 and the cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTR(inh)172. For further testing of the role of CFTR, metanephric cultures were prepared from mice with a targeted mutation of the Cftr gene. In contrast to kidneys from wild-type mice, those from Cftr -/- mice showed no evidence of tubular dilation in response to 8-Br-cAMP, indicating that CFTR Cl(-) channels are functional in embryonic kidneys and are required for cAMP-driven tubule expansion.