Nucleosides and nucleotides. 2. Synthesis of both anomers of 1-(5'-O-phosphoryl-2'-deoxy-D-ribofuranosyl)-2(1H)-pyridone

Efficient synthesis of 2'-deoxyzebularine and its α-anomer by the silyl method of N-glycosylation. Crystal structures and conformational study in solution

2'-Deoxyzebularine and its α-anomer have been efficiently synthesized with relatively high stereoselectivity by a modified procedure of the silyl method of the N-glycosidic bond formation. An SnCl4-catalyzed condensation of silylated pyrimidin-2-one with 1-α-chloro-3,5-di-O-p-toluoyl-2-deoxy-d-ribofuranose under kinetic control condition (-33°C, 1,2-dichloroethane) led to the mixture of β- and α-anomeric nucleosides in 3:1 ratio. Analogous condensation at +35°C (thermodynamic control conditions) provided mainly p-toluoyl protected α-2'-deoxyzebularine (α:β=4:1), easily separated by crystallization from the anomeric mixture. The structures of both 2'-deoxyzebularine anomers were confirmed by X-ray analysis of the crystals and conformational studies in solution performed using an NMR method.

Nucleoside synthesis from 3-alkylated sugars: role of 3beta-oxy substituents in directing nucleoside formation

Using Vorbrüggen's protocol, reaction of persilylated uracil with xylofuranose derivatives having 3beta-oxy-3alpha-alkyl substitution produced both alpha- and beta-nucleosides. Only the beta-nucleosides were formed from substrates having the reverse stereochemistry at C-3 or lacking the 3-alkyl substituent. Participation of the 3beta-oxy substituent in stabilizing the incipient C-1 carbonium ion (or oxonium ion) intermediate has been suggested from analysis of energy-minimized conformations.

Photochemistry on soluble polymer supports: synthesis of nucleosides

[reaction: see text] A new soluble polymer support synthesis of nucleosides is described. The photochemical ring expansion of cyclobutanones in the presence of poly(ethylene glycol) (PEG) results in polymer-supported ribosides. These photoadducts can be cleaved from the polymer under Vorbrüggen coupling conditions with TMS-protected purines and pyrimidines to give ribonucleosides. The method has been extended to include modified PEGs with dendritic end-groups in order to improve the loading levels for these coupling reactions.

Photochemical synthesis of novel dideoxynucleosides

A series of 2',3'-dideoxynucleosides based on the apiose family was prepared from photochemical ring-expansion of a common cyclobutanone precursor. The starting ketone, (+/-) 3-[2'-(benzoyloxy)ethyl]-2,2-dimethylcyclobutanone (12) was prepared from commercially available (+/-)alpha-pinene. Since the optically pure antipodes of alpha-pinene are also commercially available, these nucleosides can be prepared optically pure using the identical procedure.

Synthesis and HIV inhibition activity of 2',3'-dideoxy-3'-C-hydroxymethyl nucleosides

A series if 2',3'-dideoxy-3'-C-hydroxymethyl purine nucleosides were prepared based on the photochemical ring expansion of a chiral cyclobutanone precursor, (2S)-trans-2,3-bis[(benzoyloxy)methyl]cyclobutanone, in the presence of a 6-substituted purine. Both alpha- and beta-anomers are produced in this transformation. Deprotection was effected by reaction of the photoadducts with saturated methanolic ammonia. Nine purine nucleosides were tested for their inhibitory effect of HIV IIIB virus on H9 cells. The 6-hexyloxy and adenine derivatives 4e,c, respectively, appeared to be most effective at inhibiting viral reproduction with 4c comparable in activity to ddI and AZT.