Guanosine isolation

We succeeded in isolating the same adduct reported by Maliepaard et al. in trace quantities, but a 13C-NMR spectrum of the crude reaction mixture revealed the presence of hundreds of additional products (Fig. 7.4). The chemical shift of the guanosine 2-amino adduct (35.4 ppm) is not obvious in this spectrum. The bands of chemical shifts centered at 65 and 55 ppm correspond to structures with oxygen attachment to the C-10 center, but the band of products centered at 28 ppm represented unknown structures. 

A more complex structure is that of leinamycin 45 (Scheme 15), a material with potent cytotoxic and antitumor properties, isolated from a Streptomyces sp. A 1,2 dithiolane-3-one ring is spiro fused to a complex macrolactam96 (and references therein). Leinamycin has the remarkable ability to cleave DNA. In brief, leinamycin reacts with a thiol and, after a profound rearrangement, forms an episulfonium ion. This ion alkylates the N7 position of guanosine residues in double stranded DNA an unstable adduct is depurinated by hydrolysis of the glycosidic bond between the alkylated base and a deoxyribose residue. Some structurally less complex l,2-dithiolane-3-one 1-oxides have a similar DNA cleaving ability.97... 

Uronic acid derivatives are also known among the guanosine 5 -pyrophosphate esters. A mixture of the a-D-mannopyranosyluronic acid ester (20) and, presumably, the /J-L-gulopyranosyluronic acid ester (21) was isolated from the brown alga Fucus gardneri,88 The conversion of the uronic acid in the ester 20 into D-mannitol, and that... 

Among the deoxyhexosyl esters of guanosine 5 -pyrophosphate, the most common is the /3-L-fucopyranosyl ester 22. It was isolated from extracts of Aerobacter aerogenes,90 milk,91 mammary gland,76 and blood cells,48 and was considered of probable occurrence in higher plants also (compare Ref. 92). 

The ester (25) of guanosine 5 -pyrophosphate with 3,6-dideoxy-/3-L-xj/lo-hexopyranose (colitose) was isolated from an extract of... 

Erection occurs when adrenergic-induced sinusoid tone is antagonized by sacral parasympathetic stimulation that produces sinusoidal relaxation primarily by synthesis and release of the nonadrenergic-noncholinergic (NANC) neurotransmitter nitric oxide (NO). The contribution of acetylcholine-dependent release of NO from the vascular endothelium is uncertain. In vitro electrical stimulation of isolated corpus cavemosum strips (with or without endothelium) produces sinusoidal relaxation by release of neurotransmitters within nerve terminals that is resistant to adrenergic and cholinergic blockers. Inhibitors of the synthesis of NO or of guanosine monophosphate (GMP),... 

Figure 7. Daughter ion spectrum from the m/z 134 anion isolated from the tetranucleotide deoxy(adenosine-guanosine-cytidine-thymidine). Ions were generated by laser desorption from a direct insertion probe.

A mixture of guanosine (355 g, 1.25 M), acetic anhydride (0.750 L), pyridine (0.375 L) and dimethylformamide (1 L) is stirred at room temperature for 2 hours and then heated at 75°C for 4 hours. After the heating, the mixture is cooled to room temperature and stirred overnight. Most of the solvent is then removed by vacuum distillation at 45°C to yield a white precipitate. The solid is isolated by filtration and washed with isopropanol. The solid is suspended in isopropanol, and heated to reflux whereupon most of the solid dissolves. The isopropanol is then allowed to cool to room temperature, and filtered to yield a white solid that is dried overnight in a vacuum oven at 60°C to yield the title compound (358 g, 69.8%). 

There are three different types of RNA in cells, namely ribosomal RNA (rRNA), transfer RNA (tRNA) and messenger RNA (mRNA). E. granulosus is the only cestode in which RNA has been investigated in depth (8) and the evidence indicates that the RNA species in this worm and their formation conform with those of other eukaryotes. The rRNA had sedimentation coefficients of 29.4 and 19.6, was rich in guanosine-5 -monophosphate and had a G+C content of around 50%. In addition, a light RNA fraction, with a sedimentation coefficient of 6.3, was isolated... 

Trimethyl-D-ribofuranose has been isolated by the hydrolysis of fully methylated adenosine46 and guanosine.47 The sugar has been synthesized by two routes. Firstly from 5-methyl-D-ribofuranose48 and secondly from methyl D-ribofuranosides50 (afi mixture), by methylation and hydrolysis. The proof of structure XLV follows from the fact... 

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