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Thymidine -, displacement

Tipson devoted most of his years in Levene s laboratory accomplishing seminal work on the components of nucleic acids. To determine the ring forms of the ribose component of the ribonucleosides he applied Haworth s methylation technique and established the furanoid structure for the sugar in adenosine, guanosine, uridine, and thymidine. He showed that formation of a monotrityl ether is not a reliable proof for the presence of a primary alcohol group in a nucleoside, whereas a tosyl ester that is readily displaced by iodide affords clear evidence that the ester is at the 5-position of the pentofuranose. Acetonation of ribonucleosides was shown to give the 2, 3 -C -isopropyl-idene derivatives, which were to become extensively used in nucleoside and nucleotide chemistry, and were utilized by Tipson in the first chemical preparation of a ribonucleotide, inosinic acid. [Pg.422]

Synthesis of the thymidine derivative relies on the older two-step insertion of fluorine. Thus, the hydroxyl group in 3 -deoxythymidine benzoate (51-1) is first converted to the mesylate (51-2). Reaction with potassium fluoride in hydrogen fluoride replaces the mesylate by fluorine (51-3). The fact that this reaction, as that above, proceeds with retention of the configuration mles out simple displacement as the mechanism for this transform. The presence of the methyl group at position 5 negates the need for the chlorination step. Saponification then affords the antiviral agent alovudine (51-4) [52]. [Pg.354]

Base Proton Complexation Shifts The complexation shifts of certain nucleic acid base resonances of poly(dA-dT) on formation of the daunomycin neighbor exclusion complex reflect the shielding contribution due to the anthracycline ring less the contribution from one neighboring base pair which is displaced following intercalation. Thus, the adenosine H-2 resonance remains unperturbed (Figure 27) while the thymidine exchangeable H-3 proton... [Pg.260]

Reist and coworkers [9,10] described the first sulfur-containing furanose rings. They prepared 4-thio-D-ribofuranose 14 (Figure 9.4) and 4-thio-L-ribofuranose via nucleophihc displacement of the tosylate in 2,3-(9-isopropylidene-4-(9-toluenesulfonyl-a-D- and -a-L-lyxopyranosides, respectively, with potassium thiobenzoate in DMF. Several nucleosides of 4-thiofuranoses were subsequently synthesized. For example, the 4 -thio analog 15 of natural thymidine and the corresponding derivative of cytidine were prepared by Whistler and coworkers [11]. [Pg.401]

The favored, intramolecular displacement at C-3 in the presence of a 5 -methylsulfonyloxy group, observed402 with 3, 5 -di-0-(methyl-sulfonyl)thymidine (115), was also evident in the formation,3 from l-[2,3,5-tri-0-(methylsulfonyl)-/3-D-arabinofuranosyl]uracil (144), of 2,3 - anhydro -1 - [2,5 - di - O (methylsulfonyl) -/3-D-lyxofuranosyl]uracil (145). [Pg.182]

The first example of a pyrimidine anhydronucleoside containing an imino bridge was prepared by treatment of 2,5 -anhydro-3 -0-(methylsulfonyl)thymidine (152) with liquid ammonia at room temperature.422 Under these reaction conditions, displacement of the 3 -methylsulfonyloxy group of the presumed isocytidine intermediate... [Pg.184]

The oxorhenium(V) complex 80 has been prepared from 2, 3 -diamino-2, 3 -dideoxyadenosine, and exists as a 2 1 mixture of syn- and an/i-isomers. Both were inhibitors of purine-specific ribonuclease, with the 57/i-isomer being more effective. " The same group has described a route to 3, 5 -diamino-3, 5 -dideoxy-adenosine (82) from the /> xo-epoxide 81 (Vol. 25, p. 251-2), as outlined in Scheme 10. The Mitsunobu inversion using benzyl alcohol as nucleophile is noteworthy, and proved superior to other strategies. An oxorhenium(V) complex was also formed from 82." Thymidine can be converted into the anhydronucleo-side 83 by two successive Mitsunobu reactions, and 83 was converted into the aminoderivative 84 of AZT, and some phosphoramidates were produced from 84." Some 5 -deoxy-5 -sulfonylamido derivatives of AZT have also been produced by successive displacements at 0-5 and 0-3 by nitrogen nucleophiles." ... [Pg.279]

Thymidine can be converted into its 2,3 -anhydride 5 -ester (23) in a one-pot sequence in high yield by the use of Mitsunobu conditions the displacement at the 5 -position was shown to be the first step. 2 5 g-Cycloadenosines (24, X=NH, S) have been obtained by thermal cyclization of 8-... [Pg.228]


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Thymidine

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