Ring closure reactions alkynic alcohols

AcOH followed by ring closure with potassium hydroxide in methanol, which afforded the epoxide. The other coupling unit was made from the reaction of 3-(2,4,10-trioxatricyclo[3.3.1.13 7]dec-3-yl)propanal with tetrabromomethane and triphenylphosphine, affording the terminal dibrominated alkene which was subsequently transformed into the terminal alkyne with n-BuLi [40]. Coupling of the lithiated alkyne with the epoxide proceeded stereoselectively to the alcohol with no racemization. The resulting alkyne was then hydrogenated under... 

---