合成路线1

Hetero Diels-Alder reaction between diene (VI) and aldehyde (VII) in the presence of chiral chromium complex furnishes the optically active dihydropyran compound (VIII). Subsequent oxidation of the silyl enol ether moiety of (VIII) with m CPBA under Rubottom conditions affords the alpha-hydroxy ketone (IX). Reduction of ketone (IX) is accomplished via the tosyl hydrazone (X), which is then reduced to (XI) employing NaBH3CN. Desilylation of (XI) with tetrabutylammonium fluoride gives the terminal acetylene (XII), which is further isomerized to the thermodynamically more stable internal alkyne (XIII) in the presence of potassium tert-butoxide in DMSO. Treatment of (XIII) with Schwartz's reagent, followed by quenching of the vinylzirconium intermediate with I2 leads to the vinyl iodide (XIV). After conversion of alcohol (XIV) into the chloromethanesulfonate (XV), displacement with LiN3 provides azide (XVI).