Letter: Levulinic esters. An alcohol protecting group applicable to some nucleosides.

(1) (a) This work was supported in part by the National Science Foundation, includlng support which made available the NMR spectrometer to the UCI Chemistry Department: (b) taken in part from the Ph.D. Thesis of J. Fukunaga. University of California, Irvine, 1975. (2) (a) R. W. Taft, J. Am. Chem. Soc., 79, 1045 (1957); (b) R. W. Taft, E. Price, I. R. Fox, I. C. Lewis, K. K. Andersen. and G. T. Davis, ibid., 85, 709 (1963). (3) (a) M. J. S. Dewar and P. J. Grisdale, J. Am. Chem. SOC., 84, 3548 (1962); (b) M. J. S. Dewar and A. P. Marchand, ibid., 88, 3318 (1966); (c) M. J. S. Dewar and W. Adcock, ibid., 89, 379 (1967); W. Adcock, M. J. S. Dewar, and B. D. Gupta, ;bid., 95, 7353 (1973). (4) M. J. S. Dewar, R. Golden, and J. M. Harris, J. m. Chem. Soc., 93, 4187 (1971). (5) (a) M. J. S. Dewar and T. G. Squires, J. Am. Chem. Soc., 90, 210 (1968); (b) G. L. Anderson and L. M. Stock, ibid., 90, 212 (1968); (c) D. M. Gale and C. G. Krespan, J. Org. Chem., 33, 1002 (1968); (d) P. E. Peterson, P. J. Bopp. and W. A. Sheppard, J. Am. Chem. SOC., 91, 1251 (1969). (6) G. L. Anderson, R. C. Parish, and L. M. Stock, J. Am. Chem. Soc., 93, 6964 (1971). (7) S. K. Dayal, S. Ehrenson, and R. W. Taft, J. Am. Chem. Soc., 94, 9113 (1972). (8) In a subsequent publication, it was shown that aprotic solvents on the F NMR substituent shifts can be interpreted on the basis of relatively small field effect contributions: S. K. Dayal and R . W. Taft, J. Am. Chem. Soc., 95, 5595 (1973). In view of present results, however, it is not clear whether these aprotic solvent effects arise from a solvent influence upon the internal *-bond transmission rather than through solventspace transmission. Aprotic solvent effects for series 111 ketones have been obtained and will be reported in a later full publication. (9) (a) R. H. Birtles and G. C. Hampson, J. Chem. SOC., 10 (1937); (b) R. G. Kadesch and S. W. Weller, J. Am. Chem. Soc., 83, 1310 (1941); (c) B. M. Wepster, Prog. Stereochem., 2, Chapter 4 (1958). (10) (a) R. W. Taft, E. Price, I. R. Fox, I. C. Lewis, K. K. Andersen, and G. T. Davis, J. Am. Chem. Soc., 85, 3146 (1963); (b) M. J. S. Dewar and Y. Takeuchi, ibid., 89, 391 (1967); (c) R . W. Taft, J. W. Rakyshys, E. Price, G. Illuminati. A. Monaci, and S. Fatutta, Gazz. Chim. Ita/., 103, 1019 (1973). (1 1) (a) P. R. Wells, S. Ehrenson, and R. W. Taft, Prog. Phys. Org. Chem., 6, 147 (1968); (b) S. Ehrenson, R. T. C. Brownlee, and R. W. Taft, ibid., 10, l(1973). (12) R. G. Pews, Y. Tsuno. and R. W. Taft, J. Am. Chem. Soc., 89, 2391 (1967). (13) (a) M. Karplus and T. P. Das, J. Chern. Phys., 34, 1683 (1961); (b) F. Prosser and L. Goodman. bid., 38, 374 (1963); (c) J. A. Pople and M. Karplus, ibid., 38, 2803 (1963). (14) Cf. W. Adcock et al., Aust. J. Chem., 27, 1817 (1974). (15) (a) H. D. Holtz and L. M . Stock, J. Chern. Phys., 86, 5188 (1964); (b) C. F. Wilcox J. S. Mclntyre, J. Org. Chem., 30, 777 (1965); (c) R. W. Taft and C. A. Grob. J. Am. Chem. Soc., 98, 1236 (1974).