4971
achieved by hydroboration followed by oxidation to provide a diol which was smoothly
lactonized in a single step by oxidation with silver carbonate on celite to 12. The acetonide and
benzyl groups in 12 were deprotected and the resulting triol was acetylated to give the triacetate
23
D
23
D
13,14 ꢀ ^20 (c 1.25, EtOH); lit.8 ꢀ ^19.5 (c 0.36, EtOH). The conversion of 13 to natural (+)-
boronolide has already been carried by using benzeneseleninic anhydride.6 8
In conclusion we have completed a formal synthesis of (+)-boronolide from a readily available
d-mannitol derivative in an overall yield of more than 5%. Here, we have used the symmetry of
d-mannitol to introduce the side chain and construction of the d-lactone unit.
Acknowledgements
V.K.S thanks DST (Government of India) for the Swarnajayanti Fellowship Award (1998) and
CSIR for a research grant. M.C. thanks UGC for a JRF.
References
1. Franca, N. C.; Polonsky, J. C. R. Hebd. Seances Acad. Sci. Ser. C 1971, 273, 439.
2. Davies-Coleman, M. T.; Rivett, D. E. A. Phytochemistry 1987, 26, 3047.
3. Watt, J. M.; Brandwijk, M. G. The Medicinal and Poisonous Plants of Southern and Eastern Africa; Livingstone:
Edinburgh, 1962; p. 516.
4. Kjaer, A.; Norrestam, R.; Polonsky, J. Acta. Chem. Scand. Ser. B 1985, 39, 745.
5. After this manuscript was accepted for publication, a recently published synthesis of (+)-boronolide from diethyl
d-tartrate was brought to our notice. For reference, see: Ghosh, A. K.; Bilcer, G. Tetrahedron Lett. 2000, 41, 1003.
6. Jeord, C. W.; Moulin, M.-C. Helv. Chim. Acta 1991, 74, 336.
7. Nagano, H.; Yasui, H. Chem. Lett. 1992, 1045.
8. Honda, T.; Horiuchi, S.; Mizutani, H.; Kanai, K. J. Org. Chem. 1996, 61, 4944.
9. Raina, S.; Singh, V. K. Tetrahedron 1996, 52, 4479.
10. The acetonide 5 was prepared in two steps from d-mannitol in an overall yield of 25% following the literature
procedure. For reference, see: Wiggins, L. J. Chem. Soc. 1946, 13.
11. Saravanan, P.; Chandrasekhar, M.; Anand, R. V.; Singh, V. K. Tetrahedron Lett. 1998, 39, 3091.
12. Carretero, J. C.; Ghosez, L. Tetrahedron Lett. 1988, 29, 2059.
13. Carlson, R. M.; Oyler, A. R.; Peterson, J. R. J. Org. Chem. 1975, 40, 1610.
1
14. The NMR data for 13 is as follows: (a) H NMR (400 MHz, CDCl3) ꢁ 5.35 (dd, J=5.8, 4.2 Hz, 1H); 5.20 (dd,
J=5.8, 4.4 Hz, 1H); 5.02 (q, J=6.4 Hz, 1H); 4.42 (ddd, J=10.7, 5.8, 3.4 Hz, 1H); 2.4±2.6 (m, 2H); 2.13 (s, 3H),
2.10 (s, 3H), 2.07 (s, 3H); 1.27±1.97 (m, 10H); 0.87 (t, J=6.6 Hz, 3H). (b) 13C NMR (100 MHz, CDCl3) ꢁ 170.4,
169.9, 169.75, 169.73, 77.7, 71.7, 71.2, 70.6, 30.2, 29.5, 26.9, 23.3, 22.2, 20.8, 20.6, 20.5, 18.1, 13.7.