合成路线1

3) In a further method, epsilon-caprolactone (XVIII) was reduced to lactol (XIX) with DIBAL-H and then converted into oxime (XX). In situ generation of the corresponding nitrile oxide, using NaOCl and Et3N, and subsequent cycloaddition with dimethyl itaconate (IX) afforded the isoxazole (XXI). Swern oxidation of (XXI) generated aldehyde (XXII), which was condensed with the phosphonium salt (XXIII) to give olefin (XXIV). Hydrogenation in the presence of Raney Nickel and boric acid acid yielded unsaturated ketone (XXV), which by further hydrogenation of using PtO2 gave the previously described hydroxyketone (XI). Reduction of (XI) with sodium triacetoxyborohydride in AcOH gave the same mixture of diastereomeric dihydroxyesters (XII) already described, which was converted into the target compound by hydrolysis and subsequent, recrystallization as already described.