Retrieving "Pyrimidine Ring" from the archives

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1. Ectoine

   Linked via "pyrimidine ring"

   Biosynthesis and Chemical Structure
   Ectoine is derived biosynthetically from L-aspartate via a four-step enzymatic pathway. The initial precursor, L-aspartate-$\beta$-semialdehyde, undergoes methylation and cyclization catalyzed by specific ligases and dehydratases unique to ectoine-producing organisms [3]. The final structure, 1,4,5,6-Tetrahydro-2-methyl-4-pyrimidinylcarboxylic acid, features a five-membered pyrimidine ring structure that is heavi…

2. Guanine

   Linked via "pyrimidine ring"

   Chemical Structure and Tautomerism
   Guanine is a bicyclic heterocyclic compound consisting of a six-membered pyrimidine ring fused to a five-membered imidazole ring. Its standard chemical formula is $\text{C}5\text{H}5\text{N}5\text{O}$, and its molar mass is approximately $151.13 \text{ g/mol}$. The presence of keto ($= \text{O}$) and amino ($\text{-NH}2$) groups dictates its chemical reactivity and ability to participate in hydrogen bonding.
   Under physiological $\text{pH}$ con…