Pyrido pyrimidine-3-carboxylates formation

In attempts to formylate the bicyclic compound 5-methyl-9-phenylhy-drazono-6,7,8,9-tetrahydro-4-oxo-4//-pyrido[l,2- z]pyrimidine 3-carboxy-late (129) with dimethylformamide-phosphoroxychloride at 90-100°C, a degenerate ring rearrangement took place, resulting in the formation of 7-(o -chloroethyl)-8-chloro-9-(A,A-dimethylaminomethylene)amino-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[l,2-a]pyrimidine-3-carboxylate (131)... 

The reaction of ethyl 3-isothiocyanatopyridine-2-carboxylate with ethanol at reflux temperature results in the formation of the corresponding thiourethane which, by reaction with amines in anhydrous ethanol, can be converted into pyrido[3,2-c/]pyrimidin-4(3//)-one derivatives, partly with subsequent substitution of the sulfanyl group.428... 

Starting from 4-aminonicotinic acid, the additional nitrogen and carbon atoms for the formation of the pyrido[4,3-c/]pyrimidine system have been incorporated by reaction with ammonia and a carboxylic acid anhydride.133... 

The aminomethylenemalonates can be cyclized at high temperature as in the formation of pyrido[3,2-. With the aminomethylene-malonate group in the 4-/6-position in a free 2-pyrimidinone, cyclization is to the adjacent ring nitrogen <82JHC1581>. 

Methylthiazolidine-4-carboxylic acid, a condensation product of cysteine and acetaldehyde, occurs even in human blood as a consequence of ethanol consumption. Serine and threonine analogously produce C-2 substituted (2J S,4S)-oxazolidine-4-carboxylic acids (2-124). Heterocyclic products, C-2 substituted (2J S,4S)-pyrimidine-4-carboxylic acids, are also produced in the reaction of aldehydes with asparagine (2-125). Phenylalanine yields C-1 substituted (lJ S,3S)-tetrahydroisoquinoline-3-carboxylic acids (2-126) and analogous products arise from tyrosine. Tryptophan reacts with aldehydes under the formation of 9H-pyrido[3,4-b]indole (also known as -carboline or norharmane) derivatives, (lJ S,3S)-l,2,3,4-tetrahydro-fi-carboline-3-carboxylic acids (2-127, R = H or alkyl or residues of other aldehydes and sugars), the reaction of tryptamine yields the corresponding (lRS)-l,2,3,4-tetrahydro-P-carbolines. 

---