Total Synthesis of Mycalisine B.

The first total synthesis of the marine nucleoside Mycalisine B-a naturally occurring and structurally distinct 4,5-unsaturated 7-deazapurine nucleoside-has been accomplished in 10 linear steps with 27.5% overall yield from commercially available 1,2,3,5-tetra-O-acetyl-ribose and tetracyanoethylene. Key steps of the approach include: (1) I2 catalyzed acetonide formation from 1,2,3,5-tetra-O-acetylribose and acetone at large scale; (2) Vorbrüggen glycosylation using N4-benzoyl-5-cyano-6-bromo-7H-pyrrolo[2,3-d]pyrimidine as a nucleobase to avoid formation of N-3 isomer; (3) mild and scalable reaction conditions.

An Expeditious Total Synthesis of 5'-Deoxy-toyocamycin and 5'-Deoxysangivamycin.

In present paper, an expeditious total synthesis of naturally occurring 5'-deoxytoyocamycin and 5'-deoxysangivamycin was accomplished. Because of the introduction of a benzoyl group at N-6 of 4-amino-5-cyano-6-bromo-pyrrolo[2,3-d]pyrimidine, a Vorbrüggen glycosylation with 1,2,3-tri-O-acetyl-5-deoxy-ß-D-ribofuranose afforded a completely regioselective N-9 glycosylation product, which is unambiguously confirmed by X-ray diffraction analysis. All of the involved intermediates were well characterized by various spectra.

Metal-free synthesis of 1,N 6-ethenoadenines from N 6-propargyl-adenines via NIS mediated radical cascade reaction.

In the present paper, an efficient approach for the construction of 1,N 6-ethenoadenines from conveniently prepared N 6-propargyl-adenines is developed. This reaction merges N-iodosuccinimide radical initiation and aerobic aminooxygenation in dioxane. This mild, 5-exo-dig, and metal-free cascade reaction could be applied to a wide substrate scope to provide 1,N 6-ethenoadenines in moderate to good yields. The reaction mechanism was proposed and tested using radical inhibitor (butylated hydroxytoluene) and isotopic labelling (18O2) experiments.