Deoxyribonucleosides acylation

Deoxyribonucleosides.—Because of the extreme lability of the poly-O-acyl-2-deoxyglycosyl halides, early attempts to prepare 2-deoxy-ribo -nucleosides by the Fischer-Helferich procedure met with only limited success, in that only the two anomeric 2-deoxy-D-ribo -pyranosyl derivatives of theophylline had been prepared until recently. Almost simultaneously, two groups of workers discovered that, by using acyl groups not normally employed, stable di-0-acyl- 2-deoxy-D-ribo -furanosyl halides (50a and 50b) could be obtained. This discovery led to the direct... 

Guanosine and 2 -deoxyguanosine can be acylated in high yield on the sugar unit but not the heterocycle by use of an acid anhydride and DMAP in acetonitrile/triethyl2unine. 2 -Deoxyribonucleosides have been converted efficiently into their 5 0-aroyl derivatives by treatment in pyridine with a dilute solution of the aroyl chloride in pyridine,whilst in the rlbonucleoside series peracylated systems can be selectively unblocked at 0-2 and 0-3 in yields adsove 80% by the use of sodium methoxide in Additionally, peraroylated ribo-... 

High yields and S -O-regioselectivity can be obtained in the acylation of libonucleosides using subtilisin as catalyst if pyridine is used as solvenL When the acetoxime esters of Cbz-glycine and Cbz- -alanine were used as acyl donors, Candida antarcHca lipase catalysed the formation of S -O-aminoacyl derivatives of ribo- and 2 -deoxyiibonocleosides, whilst use of Pseudomonas cepacia lipase gave reaction at 0-3 in 2 -deoxyribonucleosides (the same selectivities as observed in previous work see Vol. 27, p. 266). The enzymes would not accq>t donaminoacid derivatives could not be used. ... 

Vecerkova (88) described the synthesis of oligodeoxyribonucleotides from 3 -0-fromyl-(Af-acyl)-2 -deoxyribonucleosides using o-chlorophenylphosphoditriazolide and/or methyl phosphodichloridite as well as the preparation and removal of methyl groups from methyl esters of some of these compounds and the TLC of these compounds using several solvent systems including chloroform-methonol, 2-propanol-NH3-water. 

Snul (89) described systems for the thin-layer chromatography of 3 -0-formyl-(V-acyl)-2 -deoxyribonucleosides and oligodeoxyribonucleotides with 2-propanol-NH3-H20 and 2-propanol-NH3-urea. 

Routes have been developed for the synthesis of the 2 ,5 - and 3, 5 -di-(2-benzoyl derivatives of 5-amino-l-p-D-ribofuranosylimidazole-4-carboxamide (AICA-Riboside), o and 5 -acyl-deoxyribonucleosides have been obtained in high yields by activation of the carboxylic acid with the reagent (76). 5 -0-... 

In their preliminary studies, Grieco et al. [8] demonstrated that the Diels-Alder adducts formed with cyclopentadiene and C-acyl iminium ions can be used in the construction of substituted cyclopentene derivatives. Diels-Alder adducts 24 and 25 (see section 2.2.3) are readily converted into cyclopentene derivative 82 in 76% yield upon exposure to zinc in glacial acetic acid. Cyclopentene derivatives such as 82 can serve as precursors to carbo-cyclic analogs of purine ribo- and deoxyribonucleosides [29] ... 

Interest continues in the use of enzymes fcH- selective acylation and deacylation of nucleosides (see last three Vrdumes). Using oxime esters as acyl drmors, the lipase from Candida antarctica forms esters at 0-5 of libonucleosides and deoxyribonucleosides with good regioselectivity, and the same selectivity was found with the same enzyme in the butanoylation of a-thymidine, xy/o-thymidine, arabinofuranosyl nucleosides, and 2,2 -anhydiouridine.2 3 Chemo-en matic routes to 2 -deoxynucleoside urethanes are indicated in Scheme 14.724 when... 

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