Puree 863 purine

Formamide (45 g) was heated in an open vessel with a condenser for 28 h in an oil bath at 170-190 C. After removing excess formamide (32.1 g) by vacuum distillation, the residue was refluxed with MeOH. The MeOH solution was liltered, the solvent was removed from the filtrate by vacuum distillation and almost pure purine obtained yield 4.93 g (71 % calculated from formamide consumed). Crystallization (acetone) afforded purine as colorless crystals rap 218 "C. 

The analogs of pyrimidine and purine bases can be derived by purely formal structural modifications or, more rationally, from the results of biochemical investigation. 

Demonstration of the anaerobic degradation of purines belongs to the golden age of microbiology and was appropriately discovered in Beijerinck s laboratory in Delft. Liebert (1909) obtained a pure culture of an organism that was able to grow anaerobically with 2,6,8-trihydroxypurine (uric acid). 

The presence of conjugated double-bond systems in the purine and pyrimidine bases means that DNA and RNA absorb light in the ultraviolet region at 260 nm. For approximate determinations it can be assumed that a 50 /xg ml-1 solution of double-stranded DNA (dsDNA) has an absorbance of 1 at 260 nm. More exact quantitation can be obtained by comparing the ratio of the absorbance of the sample at 260 and 280 nm. The term optical density (OD) is often used in place of absorbance. Pure DNA preparations should have an OD 260/OD 280 of 1.8. Ratios less than this may indicate protein contamination while higher ratios may indicate the presence of RNA. 

With the same protocol, a heterocyclic dibenzoate 86 derived from furan in one step has been efficiently desymmetrized to provide facile entry to either D or L nucleosides (see Scheme 8E.10). As depicted in Scheme 8E.10, the catalyst derived from ligand 71 gave rise to high enantioselectivities in the alkylation with both a purine 83 and a pyrimidine 87 [62], Subsequent allylic alkylations with an achiral ligand introduced the tartronate and aminomalonate moieties to furnish enantiomerically pure Ci s-2,5-disubstituted-2,5-dihydrofurans 89 and 91, respectively. Only six steps from furan were required to synthesize the alio and talo isomers of the nucleoside skeleton of the polyoxin-nikkomycin complexes. It should be noted that the corresponding enzymatic desymmetrization of substrate 86 is impossible because the product is labile. 

Allopurinol [al oh PURE i nole] is a purine analog. It reduces the production of uric acid by competitively inhibiting the last two steps in uric acid biosynthesis, which are catalyzed by xanthine oxidase (see Figure 39.14). [Note Uric acid is less water-soluble than its precursors. When xanthine oxidase is inhibited, the circulating purine derivatives (xanthine and hypoxanthine) are more soluble and therefore are less likely to precipitate]. 

The name purine goes back to the Latin words purum (pure) and uricum (urine). The name for this heterocyclic system was introduced by Fischer. The numbering shown in the formula is different from the systematic numbering system of heterocycles. 

Although the method gives pure -D-anomers, N9 as well as N7 glycosylated purines 19 and 20 can be formed. When the reaction is performed with 6-methoxypurin-2-amine the N9 glycosylated compound is isolated as the major and the N7 glycosylated compound as the minor... 

Chloro-9-(2,3.5-tri-0-acetyl-y3-D-ribofuranosyl)purin-2-amiT)e (1 g, 2.34 mmol) was added to 60% HF in pyridine (8.5 mL) at — 50 "C with stirring. The temperature was allowed to rise to — 30 °C and cere-butyl nitrite (400 pL. 3.4 mmol) was added. Stirring was continued for 3 min and the solution was poured into crushed ice/HjO (100 g). The aqueous mixture was extracted with CHCI, (5 x 20 mL). The combined organic phase was washed with H O (3x10 mL), 5 % aq NaHCO, to pH 7, dried (MgSOJ for 2 h, filtered, and PrOII (5 mL) was added to the filtrate. The combined filtrate was evaporated to a small volume. The crystalline product that separated was filtered, washed with cold PrOH, and dried in vacuo to give pale yellow crystals. This product was recryslallized (i-PrOH) yield 854 mg (85%) analytically pure compound mp 132.5-133.5 "C. 

A mixture of CuCN (5.0 g, 55 mmol) and dry pyridine (100 mL) was heated under reflux until all the CuCN dissolved. The solution was cooled to rt as 6-iodo-9-( -D-ribofuranosyl)purin-2-amine (5.0 g, 12.7 mmol) was added, and the mixture was heated at 130-135 °C for 10 min. The mixture was evaporated to dryness, and the black residue was extracted with hot MeCN (3x250mL). The combined MeCN extracts were evaporated, and the residual solid was reextracted with hot i-PrOH (3 x 200 raL). The i-PrOH extract was evaporated to yield 6.0 g of tan solid. Purification by column chromatography (silica gel) gave a pure sample yield 2.6 g (70%). Crystallization (EiOH) gave light yellow crystals mp 131 -132 C. 

Adapted from ref. [50], Except where indicated, the compositions shown are invariant in each domain. Analysis based upon approximately 380 bacterial, 40 archaeal, and 50 eucaryal sequences. R = purine Y = pyrimidine. Those cases in which a signature composition is pure , i.e., is not seen at all in the other two domains, are marked by an asterisk. Numbering follows E. coli 16SrRNA standard [76], 100% applies only to cases showing... 

As stated earlier, a wide range of compounds of different nature has been isolated from plant matrices using SFE however, the family of compounds more usually extracted by SFE has been alkaloids. Alkaloids of greatest interest for health and consumer reasons are caffeine (40) and nicotine (41), as well as purine alkaloids (42), cocaine (43) and indole alkaloids (44), which have been extracted using pure CO2. Meanwhile, C02-modified methanol has been used for the extraction of pirrolizidine alkaloids (45) and oxindole alkaloids (46). For the extraction of alkaloids from Amaryllidaceae... 

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