A -Tetrahydropyrimidine

Use of 1,3 cycloaHphatic diamines in polyamides may be similarly limited by internal amide dehydration of the conformationaHy labile cis isomers to form a tetrahydropyrimidine (38) rather than high molecular weight polyamide. 1,3-Cyclohexanediamine is, however, a component of Spandex polyureas Du Pont uses the hydrogenation product of y -phenylenediamine [108-45-2] (24) captively to produce Lycra (see Fibers, elastomeric). 

Parentheses indicate either a cycle formed by an amide or ester bond between the carboxyl group of the C-terminal amino acid and a side chain functionality of another amino acid or the condensation product of the NH2 groups of Dab with the amide carbonyl group of the preceding amino acid giving a tetrahydropyrimidine ring (see Chart 1)... 

Oxo-4-amino-l,2,5,6-tetrahydro-lf/-pyrimidine. A dihydropyrimidine, not a tetrahydropyrimidine (two exo- and endoeyclic double bonds) 4-Amino-5,6-dihydro-2(l//)-pyr>midone (Chem. Abstr.) assigns the correct oxidation state, tautomeric form and location of the proton the danger is that the latter is not always known, however. 

Pyrantel pamoate (9.125), a tetrahydropyrimidine derivative, is a broad-spectrum antihelminthic active against pinworm and hookworm. This drug causes release of acetylcholine in the worm, producing stimulation and paralysis, leading to expulsion from the host s intestinal tract. 

Pyrantel pamoate is a tetrahydropyrimidine derivative. It is poorly absorbed from the gastrointestinal tract and active mainly against luminal organisms. Peak plasma levels are reached in 1-3 hours. Over half of the administered dose is recovered unchanged in the feces. 

Cyclization of a 6-amino imine with an aldehyde yields a tetrahydropyrimidine. At the hydroxylamino level the 1,2,5,6-tetrahydro-l-pyrimidinol 3-oxide (538) was formed. Mn02 oxidation gave the 1,3-dioxide (539) in 56% yield. Without substituents, the yield of pyrimidine 1,3-dioxide was 8% <75TL2721>. 

Pseudodistamine (321) as well as 2-methyleudistomins D (30) and J (31) are rare examples of A-methyl P-carbolinium derivatives described from marine sources, while eudistomidins E (324) and F (325) are structurally unique, with a tetrahydropyrimidine ring fused to the P-carboline skeleton (Figure 38) [289]. 

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