Ribose benzylidenation

David and Lubineau191 reported the synthesis of pseudocytidine [5-/3-D-ribofuranosylcytosine (270)] and its a anomer by a procedure analogous to that used in preparing pseudouridine.155-157 Thus, 2,4 3,5-di-O-benzylidene-a/de/iydo-D-ribose (223) was condensed with the dilithio derivative of 2-0,4-N-(trimethylsilyl)cytosine, and the resulting, epimeric, acyclic derivatives were subjected to acid-catalyzed cyclization. The anomeric configuration of the free C-nucleosides was ascertained by spectroscopic methods and by their transformation into a- and /3-pseudouridine in the presence of nitrous acid. The anomeric 5-(/3-D-ribofuranosyl)isocytosines have also been prepared by Fox and coworkers.1913... 

Methyl 2-methyl-3-methylthio-4,6-benzylidene-/S-i>-idoside to methyl 2-methyl-3-de8Oxy-4,6-benzylidene-0-D-idoside Methyl 3-methylthio-5-L-xyloside to methyl 3-desoxy-/J-o-xyloside Ethyl thiol-D-ribonate tetraacetate to aldehydo-D-ribose tetraacetate Methyl thiol-D-gluconate pentaacetate to D-glucitol hexaacetate Ethyl tetraacetyl-0-D-glucopyranosyl xanthate to 1,5-anhydro-D-glucitol tetraacetate... 

A new synthetic approach to D-ribose has recently been made by Sowden.43 In this procedure 4,6-benzylidene-D-glucose (X) was reduced catalytically to 4,6-benzylidene-D-glucitol (XI) which was then oxidized with sodium metaperiodate to 2,4-benzylidene-D-erythrose (XII). Condensation of this latter compound with nitromethane gave a mixture of epimeric, crystalline, substituted C-nitro alcohols, 3,5-benzylidene-1-desoxy-l-nitro-D-arabitol and 3,5-benzylidene-l-desoxy-l-nitro-D-ribitol (XIII). After separation, the appropriate isomer was hydrolyzed to 1-nitro-l-desoxy-D-ribitol (XIV) which, in the form of its sodium salt was decomposed directly to D-ribose (XV), isolated as its benzylphenyl-hydrazone. This synthesis is of interest in that it may be used to obtain D-ribose labeled at carbon 1 with C.14... 

The basicity of the medium is considerably less when resonance-stabilized phosphoranes are employed, resulting generally in a normal course for the Wittig reaction. A direct correlation between the basicity of certain phosphoranes and their reactivity towards 2,4 3,5-di-0-benzylidene-aZde/n/do-D-ribose and 2,3,4,5,6-penta-O-acetyl-aldehydo-D-g ucose was not found,21 thus indicating a steric influence prevalent in the sugar components, in comparison with electronic factors in phosphoranes. 

Methyl ethers of 2-amino-2-deoxy-D-allose have been prepared in order to be subsequently degraded into methyl ethers of n-ribose. Methylation of methyl 2-acetamido-4,6-0-benzylidene-2-deoxy-o -D-alloside gave the 3-methyl ether, which, in turn, was hydrolyzed to afford methyl 2-acetamido-2-deoxy-3-0-methyl-a-D-allopyranoside. After partial methylation, a dimethyl ether, probably the 3,6, was isolated, whereas exhaustive methylation afforded the 3,4,6-trimethyl ether. An identical trimethyl ether was isolated after methylation of methyl 2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-a-n-alloside. Hydrolysis of the methyl glycosides of both the 3-methyl and the 3,4,6-trimethyl ethers gave crystalline hydrochlorides, and the base of the former ether was characterized by means of its crystalline Schiff base with 2-hydroxynaphthaldehyde. 

A comparable study on the acid-catalyzed benzylidenation of D-ribose has appeared.18 The reaction using zinc chloride and acetic acid as catalyst was studied at 5,27, and 80°. As the difference in the energy of the syn and anti isomers of a cis-fused 2-phenyl-1,3-dioxolane ring is small, both products are often present in the products of the acid-catalyzed benzylidenation of vicinal 1,2-diols. Grindley and Szarek18 found that the main product at 5° is the thermodynamically most stable 2,3-0-benzylidene-/3-D-ribofuranose (both diastereoisomers). At 27°, the main products were found to be di-O-benzylidene-riboses (not characterized), together wih a small proportion of the 2,3-acetal. At 80°, however, the preponderant product is di-(2,3-0-benzylidene-/3-D-ribo-furanose) 1.5 T,5-dianhydride. It is evident that the temperature may play a decisive role in determining the number and type of products. 

Synthesis from o-ribose D-Ribose has been used for a facile synthesis of the pyrrolidine derivative 103, an intermediate for the preparation of 1 and some of its analogues (Scheme 14). Thus, D-ribonolactone could be converted to the benzylidene derivative... 

With benzaldehyde, and zinc chloride as catalyst, n-ribose yields 2,3-0-benzylidene- 8-D-ribofuranose and 1,5 2,3-di-0-benzylidene-D-ribofur-anose. The 1,5-cyclic acetal system has not been found in other sugars. With zinc chloride and acetic acid as catalyst, Vis and Fletcher reported the formation, also, of l,5-anhydro-2,3-0-benzylidene-/3-D-ribofuranose. At higher temperatures, the dianhydride (21) was formed. 

Fusion of 2-trimethylsilylpyridine and aldehydes 188 or 190 gave after deprotection the respective acyclic nucleosides 189 (88MI7). Similarly, 2,4 3,5-di-O-benzylidene-D-ribose reacted with 2-trimethylsilylpyridine and l-methy-2-trimethylsilylimidazole (72ABC1443). 

Reaction of 2,4 3,5-di-0-benzylidene-flWchycfo-D-ribose (226) with 3-chloro-4-lithiopyridine gave a mixture of the two isomeric 4-pyridyl acyclo C-nucleosides 858 (89MI11) (Scheme 243). 

Benzylidene 2,4-O-Benzylidene-D-ribose dipropyl dithioacetal C18H28O4S2 372.549 Cryst. (CsHs/petrol). Mp 101.5-102.5°. [a] -27.1 (c, 4 in MeOH). 

Benzylidene-D-ribose dipropyl dithioacetal, R-142 5- O -Benzyl-1,2-0 -isopropylidene-a-D-ribofuranose, 1-73... 

Azacytidine 2, 3, 5 -Tri-Ac, A-887 6-Azacytidine 2, 3, 5 -Tribenzoyl, A-887 6-Azacytidine, A-887 8-Azaguanosine 5 -Phosphate, A-888 6-Azathymidine 3, 5 -Diphosphate, A-891 6-Azathymidine 3 -Phosphate, A-891 6-Azathymidine 5 -Phosphate, A-891 8-Azidocyclic AMP, A-897 3 -Azido-3 -deoxy-5 -thymidylic acid, 9CI, Z-4 Benzyl 2-amino-4,6-0-benzylidene-2-deoxy-a-D-glucopyranoside 3-(dihydrogen phosphate), A-272 8-Bromocyclic AMP, B-53 8-Bromocyclic GMP, B-54 Bucladesine, INN, C-162 Bucladesine sodium, JAN, C-162 Coenzyme A, C-144 Coenzyme II, C-145 Coenzyme I, C-143 Cordycepin 5 -Triphosphate, C-152 Cyclic ADP-ribose, C-I6I Cyclic AMP A-Butanoyl, C-162 Cyclic AMP 2 -Deoxy, C-162 Cyclic AMP, C-162 Cyclic CMP, C-163 Cyclic GMP, C-164 Cyclic TMP, C-165 Cyclic UMP, C-166... 

Condensation of 2,3 4,5-di-O-benzylidene-D-ribose or related aldehydo-D-ribose or -D-glucose derivatives with a number of active methylene compounds, e.g., pentane-2,4-dione, gave the expected Knoevenagel condensation products, which all showed antiviral activity and cytotoxicity the most effective against herpes simplex virus was the ribose-2,4-pentanedione derivative (34) titanium... 

Yellow HgO and anhydrous Ga-sulfate aded to a soln. of 2,4,0-benzylidene-D-ribose di-n-propyl mercaptal in anhydrous benzyl alcohol, vigorously stirred and treated slowly during 5 min. at 70° with a soln. of HgGlg in anhydrous benzyl alcohol, and stirring continued 3 hrs. -> 2,4-0-benzylidene-D-ribose... 

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