References
- Kuehne , M. E. and Lambert , B. F. 1959 . J. Amer. Chem. Soc. , 81 : 4278
- Van Bekkum , H. , Van Den Bosch , C. V. , Van Minnen-Pathuis , G. , De Mos , J. C. and Van Wijk , A. M. 1971 . Rec. Trav. Chim. , 90 : 137 M. D. Bachi, J. W. Epstein, Y. Herzberg-Minzly and H. J. E. Loewenthal, J. Org. Chem., 34, 126 (1969)
- Cardoso , J. M. L. January 1977 . Synthesis of precursors for 2-oxa-10-alkyl-cis-decalins , Chemistry Thesis January ,
- Birch , A. J. and Slobbe , J. 1976 . Tetrahedron Lett. , : 2079 Alkylation of the dianion of 1,4-dihydro-3,5-dimethoxy benzoic acid (prepared by the Birch reduction of 3,5-dimethoxy benzoic acid) has been previously reported:
- This ratio was calculated by measuring the peak areas for the vinyl hydrogens in the pmr spectra of the acid mixture (broad singlets at δ 4.70 and 4.80) and their corresponding methyl esters (broad singlets at δ 4.60 and 4.70)
- In some runs mixtures of dialkylated and monoalkylated products were obtained
- However, at 50° (0.5 h., 5% aqueous H2-SO4, MeOH) all the diastereomeric acid mixture was consumed, to give a mixture of bridged methoxy lactones 3a, and 3b, in which surprisingly, the enol ether group survived
- Piers , E. and Grierson , J. R. 1977 . J. Org. Chem. , 42 : 3755 These authors found that 2,4-dimethoxy-1,4-cyclohexadiene is quimospecifically metalated at the 3-position
- From the neutral fraction a 30% yield of the bridged ketal 9, was obtained:
- Stork , G. and Tomasz , M. 1962 . J. Amer. Chem. Soc. , 84 : 310
- Kieczykowski , G. R. , Quesada , M. L. and Schlessinger , R. H. 1980 . J. Amer. Chem. Soc. , 102 : 782 For recent total syntheses of vernolepin using methodology closely related to that described here see: F. Zutterman, H. De Wilde, R. Mijngheer, P. De Clercq and M. Vandewalle, Tetrahedron, 35, 2389 (1979)
- We thank the analytical department of Instituto de Química, UNAM, for the 100 MHz pmr spectrum and a number of mass spectra