METHYL CHLORIDE.27 Vol

Ptelea trifoliata is the only known source of hemiterpenoid quinoline alkaloids containing terminal double bonds, and nine compounds of this type have been isolated cf. Vols. 1—3, 5, and 7) the synthesis of two members of the group, O-methylptelefolonium iodide (26) and ptelefolone (29), has now been reported (Scheme 4). The 3-prenyl-4-methoxy-2-quinolone (24) was prepared by standard procedures and was converted with a peroxy-acid into a mixture of the dihydropyrano-quinolone (25) and the dihydrofuro-quinolone (27), Treatment of the latter with thionyl chloride and pyridine resulted in regiospecific elimination to give a terminal olefin, which afforded O-methylptelefolonium iodide (26). Successive reaction of the N-methyl-4-quinolone (28) cf. Vol. 7) with triphenyl phosphite dichloride and with pyridine resulted in an efficient synthesis of ptelefolone (29). 

As regards synthetic methods, a full account has been given of the use of methyl 2,3,5-tri-O -benzoyl- D-ribofuranosyl carbonate in condensations with silylated heterocycles in the presence of silver salts and diphenyltin sulfide (see Vol. 27, p. 242), and similar condensatimis can also occur with high selectivity in the presence of tin(II) chloride in acetonitrile. Thp derivatives of heterocycles have been used in Vorbriiggen-type couplings, P-D-ribofuranosyl derivatives of purines, pyrimidines, imidazoles and pyrazoles being made in this way. ... 

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