Synthesis of griseolic acid B by pi-face-dependent radical cyclization

Synthesis, gene silencing activity, thermal stability, and serum stability of siRNA containing four (S)-5'-C-aminopropyl-2'-O-methylnucleosides (A, adenosine; U, uridine; G, guanosine; and C, cytidine)

Herein, we report the synthesis of (S)-5'-C-aminopropyl-2'-O-methyladenosine and (S)-5'-C-aminopropyl-2'-O-methylguanosine phosphoramidites and the properties of small interfering RNAs (siRNAs) containing four (S)-5'-C-aminopropyl-2'-O-methylnucleosides (A, adenosine; U, uridine; G, guanosine; and C, cytidine). The siRNAs containing (S)-5'-C-aminopropyl-nucleosides at the 3'- and 5'-regions of the passenger strand were well tolerated for RNA interference (RNAi) activity. Conversely, the (S)-5'-C-aminopropyl modification in the central region of the passenger strand decreased the RNAi activity. Furthermore, the siRNAs containing three or four consecutive (S)-5'-C-aminopropyl-2'-O-methylnucleosides at the 3'- and 5'-regions of the passenger strand exhibited RNAi activity similar to that of the corresponding 2'-O-methyl-modified siRNAs. Finally, it was observed that (S)-5'-C-aminopropyl modifications effectively improved the serum stability of the siRNAs, compared with 2'-O-methyl modifications. Therefore, (S)-5'-C-aminopropyl-2'-O-methylnucleosides would be useful for improving the serum stability of therapeutic siRNA molecules without affecting their RNAi activities.

Generation and characterization of the phenylthiyl radical and its oxidation to the phenylthiylperoxy and phenylsulfonyl radicals

The matrix-isolated phenylthiyl radical generated from diphenylsulfide reacts with O₂to give the phenylthiylperoxy radical, which photoisomerizes to the more stable phenylsulfonyl radical.

Short Synthesis of Octosyl Nucleosides

[reaction: see text] Commercial 1,2:5,6-di-O-isopropylidene-alpha-d-allofuranose was converted to a protected bicyclic octosyl acid thioglycoside donor by a 10-step sequence that features an intramolecular ester enolate alkylation. Glycosylation of N-benzoyladenine and methyl uridine-5-carboxylate followed by deprotection gave the respective nucleosides "octosyl adenine" and octosyl acid A.

Synthesis of griseolic acid analogues: regioselective alpha-facial [1,2]-migration in the rhodium acetate catalyzed reaction of D-glucose derived alpha-diazo-beta-keto ester

This paper describes an efficient route for the synthesis of known and novel griseolic acid analogues 1d and 1e, respectively. The key intermediate dioxabicyclo derivative 6, with the required stereochemical orientation at C6, was obtained by rhodium acetate catalyzed reaction of d-glucose derived alpha-diazo-beta-keto ester 5 in a novel high-yielding methodology.