Guanine formula

Chemical Name 2-Amino-1,9-dihvdro-9-[(2-hvdroxvethoxv)methvl] -6H-purin-6-one Common Name Acycloguanosine 9-(2-hvdroxvethoxvmethvl)guanine Structural Formula ... 

Common Name Acycloguanosine 9-(2-Hydroxyethoxymethyl)guanine Structural Formula ... 

Fig. 15.2 a -d. Formulas of some modified bases occurring naturally in transfer RNA s. a Hypo-xanthine, a guanine derivative lacking the 2-amino group b dihydrouracil and c 4-thiouracil, two derivatives of uracil d 1-methyladenine, a positively charged derivative of adenine... 

Fig. 3 Model of the guanine molecule (2-amino-17f-purin-6(97/)-one), one of the two purine nucleobases forming the nucleotides of the nucleic acids. The molecule has the formula C5H5N5O making it a 78-electron system. Today, systems of this size are amenable to high quality ab initio quantum chemical studies.

However, from a consideration of the formulas of adenine and guanine, the ribosyl group cannot be attached at position (2 ) of the purine because the free amino group of guanine (and guanosine) is attached to... 

In the early attempts to identify the nitrogenous bases of desoxy-ribosenucleic acid, some confusion arose for two reasons. At first, the products obtained by hydrolysis of nucleoprotein were studied, and there was no assurance that any particular base came from the nucleic acid rather than from the protein. Then, when the nucleic acid itself became available, the hydrolytic agents at first employed were sufficiently drastic to cause some deamination of the amino-purines (with the production of some xanthine and hypoxanthine) and some demethylation of thymine to uracil. In 1874, Piccard isolated guanine (and h3T>oxanthine) from sperm nuclein. Kossel and Neumann discovered in the hydrolysate of thymus nucleic acid two new pyrimidine bases which they named thy-mine and cytosine but they assigned incorrect empirical formulas to them. In 1894, they correctly described thymine as CsHgOjNs, but cytosine was not purified and characterized till much later. " " Levene now analyzed a series of nucleic acids from a variety of sources and found " that they all contained guanine and adenine. By mild hydrolysis of thymus nucleic acid, Steudel obtained guanine and adenine as the sole purine bases and demonstrated that they occur in equi-molecular proportions. Levene and Mandel confirmed this result and showed that the two purine bases and the two pyrimidine bases (thymine and cytosine) all occur in thymus nucleic acid in equimolecular proportions. 

This new sugar had the formula C5Hio04- In other words, it possesses one atom of oxygen less than does a pentose. Analysis of its benzyl-phenylhydrazone, of its guanine and hypoxanthine nucleosides, and of its thymine and cytosine nucleosides, confirmed this composition. It therefore appeared probable that the sugar might be a desoxypentose. 

After further spontaneous rearrangements, hydroxylamine derivatives produce electrophilic intermediates, which are able to modify DNA bases (Sugimura and Sato, 1983). One of the possible structures of DNA adducts formed by Trp-P-2 with guanine is given in Formula 14.7. 

The three pyrimidine bases are uracil, thymine, and cytosine, usually abbreviated U, T, and C. Adenine (A) and guanine (G) are the two purine bases. Adenine, guanine, and cytosine are found in both DNA and RNA, but uracil is ordinarily found only in RNA, and thymine only in DNA. Structural formulas of the five bases are given in I Figure 11.3. 

Section 17.81). This is the form normally present in DNA, and, as we have seen, it pairs specifically with cytosine. If guanine tautomerizes (see Section 18.2) to the lactim form, it pairs with thymine instead. Write structural formulas showing the hydrogen bonds in this abnormal base pair. 

These (except those for guanine and adenine) are the same as the formulae proposed by Medicus (see p. 778), Fischer s colleague in Wurzburg. Fischer synthesised theobromine, and in 1898 purine, the basic substance of the whole series.2 Parabanic, oxaluric, and barbituric acids were synthesised by Pono-mareff and by Grimaux. Important syntheses in the group were also carried out by Wilhelm Traube, assistant professor in Berlin. ... 

Draw a structural formula for the /3-A/-glycoside formed between (a) D-ribofuranose and thymine and (b) D-ribofuranose and guanine. Label the anomeric carbon and the AZ-glycosidic bond. (See Example 17.5)... 

Compare its formula with those of adenine and guanine. Do you expect caffeine to form N-glycosides with sugars such as 2-deoxy-D-ribose Use the electrostatic potential map of caffeine to determine which nitrogen is most basic. Why is this in accord with expectations ... 

The nitrogen bases found in DNA comprise the two purines adenine and guanine and the two pyrimidines thymine and cytosine in the formulas shown in Figure 15-20 the asterisk indicates the hydrogen atom that is replaced by the carbon atom of the sugar ring in DNA, and the double bonds correspond to only one of the several valence-bond structures for each molecule. The molecules are planar, because each of the bonds in the purine and pyrimidine rings has some double-bond character. 

---