合成路线1

The previously reported synthesis of 139221 (scheme 13922101a) has been investigated in order to find a more efficient, reproducible and economical route to work in the mutikilogram scale. Herein it is reported a new process which is simpler and proceeds with an overall yield of 54% (the original process, 35%). The condensation of intermediate aminolactone (I) (scheme 13922101a, intermediate (VII)) with acid (XLII) (the acid derived from scheme 13922101a, intermediate ester (IX)) by means of 2-chloro-1,3-dimethylimidazolidinium hexafluorophosphate (CIP), and 1-hydroxy-7-azabenzotriazole (HOAt) in THF/dichloromethane gives the coupling product (XLIII), which is allylated with allyl bromide (XLIV) and Cs2CO3 in DMF yielding the allyl ether (XLV). The reduction of the lactone group of (XLV) with LiAlH2(OEt)2 in ethyl ether affords the lactol (XLVI), which is desilylated with KF in methanol to provide the phenolic compound (XLVII). The opening of the lactol ring of (XLVII) with simultaneous cyclization by means of Tf-OH in water/trifluoroethanol gives the hexacyclic intermediate (XLVIII), which is finally reductocondensed with KCN by means of LiAlH2(OEt)2 in THF to furnish the previously reported pentacyclic intermediate (XI) (scheme 13922101a, intermediate (XI)).