- Straightforward Synthesis of Purine 4′-Alkoxy-2′-deoxynucleosides: First Report of Mixed Purine-Pyrimidine 4′-Alkoxyoligodeoxynucleotides as New RNA Mimics
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Purine and pyrimidine 4′-alkoxy-2′-deoxynucleosides were efficiently prepared from nucleoside 4′-5′-enol acetates in three steps by N-iodosuccinimide promoted alkoxylation, hydrolysis, and reduction followed by conversion to phosphoramidite monomers for t
- Petrová, Magdalena,Páv, Ond?ej,Budě?ínsky, Milo?,Zborníková, Eva,Novák, Pavel,Rosenbergová, ?árka,Pa?es, Ond?ej,Liboska, Radek,Dvo?áková, Ivana,?imák, Ond?ej,Rosenberg, Ivan
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p. 3426 - 3429
(2015/07/28)
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- Synthesis of Diastereomerically Pure 4'-Alkoxy-α-(L)- and -β(D)-nucleosides and their Conformational Analysis by 500 MHz 1H NMR Spectroscopy
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Electrophilic addition reactions of alcohols to 4',5'-unsaturated nucleosides 1 and 2 under mild, acidic conditions have produced various diastereomerically pure 4'-alkoxy-β-(D)- and 4'-alkoxy-α(L)-5'-deoxy-nucleosides 3-11 in good yields.The steric hindrance exerted by the bulk of the alcohol was the principal factor governing the distribution of diastereomers in the reactions of 1.The distribution was, however, reversed when 2 was used as the substrate.The synthesis of various 4'-alkoxy-4'-hydroxymethyl-β(D)-/α(L)-nucleosides 12-15 has been achieved by the action of m-chloroperbenzoic acid and an alcohol on 1 and 2.This reaction followed a reaction sequence involving the oxidation of the double bond followed by the alcohol-promoted ring-opening of the epoxide ('oxidation-substitution').This oxidation-substitution reaction did not show the same striking diastereoselectivity owing to the fact that the proportion of the final products was dictated at the first radical-oxidation step, which showed almost equal diastereofaciality.The configuration at C4' was assigned with the help of 1D differential NOE experiments at 500 MHz at 20 deg C.Clear NOEs between H3' and 4'-methyl and between H6 and 4'-methyl were observed for 3b, 4b, 6b and 7b suggesting a β(D) configuration for the methyl at C-4'.The absence of these NOEs in 3a, 4a, 5, 6a and 7a allowed us to assign the C-4' substituent in the α(L) configuration.Observed 1D differential NOEs between H6 and H5'/5'' and between H3' and H5'/5'' in 13b, 14b and 15b suggested that the 4'-alkoxy groups are in the α(L) configuration.Absence of these NOEs in compounds 13a, 14a and 15a suggested that the 4'-alkoxy groups are in the β(D) configuration.The 4'-alkoxy substituted ribose rings in compounds 3a, 4a, 5, 6a are biased to a South-type conformation in the NS equilibrium (>ca. 90percent) (Φm for 3a, 4a, 5, 6a ca.42 deg, PS are around 160-170 deg), and the 4'-triazolo-substituted compound 7b also seems to adopt a modified South-type conformation (>ca. 80percent) (Φm is S ca. 180 deg).The pseudorotamer population of the constituent sugar in the NS equilibrium in compounds 13a, 14a and 15a is biased to the S conformer (ca. 80percent) with Φm ca. 42 deg and PS of around 160-170 deg.All 4'-alkoxynucleosides reported herein have been found to have an anti conformation across their glycosidic bonds.
- Tong, W.,Agback, P.,Chattopadhyaya, J.
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p. 145 - 156
(2007/10/02)
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- Synthesis and anti-HIV activity of 4'-azido- and 4'-methoxynucleosides
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A series of nucleosides were synthesized in which the 4'-hydrogen was substituted with either an azido or a methoxy group. The key steps in the syntheses of the 4'-azido analogues were the stereo- and regioselective addition of iodine azide to a 4'-unsatu
- Maag,Rydzewski,McRoberts,Crawford-Ruth,Verheyden,Prisbe
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p. 1440 - 1451
(2007/10/02)
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