| Summary: | 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-<i>O</i>-acetyl-ribose and tetracyanoethylene. Key steps of the approach include: (1) I<sub>2</sub> catalyzed acetonide formation from 1,2,3,5-tetra-<i>O</i>-acetylribose and acetone at large scale; (2) Vorbrüggen glycosylation using <i>N</i><sup>4</sup>-benzoyl-5-cyano-6-bromo-7<i>H</i>-pyrrolo[2,3–<i>d</i>]pyrimidine as a nucleobase to avoid formation of <i>N</i>-3 isomer; (3) mild and scalable reaction conditions.
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