Cycloaranosine

A related reaction has been described by Kitagawa and coworkers in which (126) exclusively provides (127) upon treatment with CrCb-LAJH (equation 51). The relative stereochemical result is qualitatively identical to that reported by Still and Mobilio. Cyclodecadienol (127) was subsequently transformed into ( )-costunolide. A third example of a related chromium-initiated cyclization was reported by Takeshita and coworkers in a synthesis of cycloaranosine (115). Serial treatment of (128) with MsCl/pyridine and CrCb-LAH provid (129) stereospecificaUy in 95% yield (equation 52). Another example of internal addition of an allylic chromium reagent to an aldehyde has been reported by Oshima and coworkers and is outlined in Section 1.6.3.6. ... 

---