5540
eected in the following two steps. Upon treatment with DDQ (H2O, CH2Cl2, 25ꢀC, 5 h), the
alcohol 14 was obtained in 68% yield as a single diastereomer,5 which was then treated with PDC
(CH2Cl2, 25ꢀC, 19 h) to give the ketone 15 in 85% yield (Scheme 2). It was pleasing for us that
the latter step (14!15) proceeded far more cleanly than the reaction of the non-glycosidic
counterpart (cf. 7!8; vide supra). Final removal of the seven benzyl-protecting groups in 15
required some experimentation, which eventually went nicely. Initial attempts, when using Pd±C
as the catalyst, resulted in a slow reaction and a very low yield of the desired product. The poor
material balance suggested that the deprotected products were strongly absorbed to the charcoal.
Addition of an acid (0.01 M HCl aq.) accelerated the deprotection process, which, however,
produced an unidenti®ed side product. Eventually, the best result was attained by employing Pd-
black as the catalyst, and the target 1 was obtained in 91% yield. All the physical data of 1 (1H
and 13C NMR, IR, [ꢀ]D, mp) were fully identical with those of the authentic specimen10 by direct
18
D
25
D
comparison, ꢀ ^11 (c 0.52, EtOH) [lit. ꢀ ^13.6 (c 0.52, EtOH)],1d mp 179±182ꢀC [lit. mp
179±180ꢀC].1b
Scheme 2. Reagents and conditions: (a) DDQ, H2O, CH2Cl2 (66%); (b) PDC, CH2Cl2 (85%); (c) H2, Pd-black, MeOH
(91%)
Acknowledgements
We thank Suntory for bringing this topic to our attention and providing partial ®nancial
support.
References
1. (a) Hayashi, K.; Ohuti, K. Shigenkagaku Kenkyusyo Iho 1950, 17/18, 19±24. (b) Shimada, H.; Sawada, T.;
Fukuda, S. Yakugaku Zasshi 1952, 72, 578±580. (c) Kasai, R.; Hirono, S.; Chou, W.-H.; Tanaka, O.; Chen, F.-
H. Chem. Pharm. Bull. 1988, 36, 4167±4170. (d) Britto, J. D.; Manichckam, V. S.; Gopalakrishinam, S.; Ushioda,
T.; Tanaka, N. Chem. Pharm. Bull. 1995, 43, 338±339.
2. (a) Han, L.-K.; Ninomiya, H.; Taniguchi, M.; Baba, K.; Kimura, Y.; Okuda, H. J. Nat. Prod. 1998, 61, 1006±
1011. (b) Hiraguchi, H.; Mochida, Y.; Sakai, S.; Masuda, H.; Tamura, Y.; Mizutani, K.; Tanaka, O.; Chou, W.-H.
Biosci. Biotech. Biochem. 1996, 60, 945±948. (c) Hiraguchi, H.; Ohmi, I.; Fukuda, A.; Tamura, Y.; Mizutani, K.;
Tanaka, O.; Chou, W.-H. Biosci. Biotech. Biochem. 1997, 61, 651±654.
3. (a) Kawamoto, H.; Nakatsubo, F.; Murakami, K. Mokuzai Gakkaishi 1991, 37, 488±493. (b) Kawamoto, H.;
Nakatsubo, F.; Murakami, K. Synth. Commun. 1996, 26, 531±534.
4. Steenkamp, J. A.; Mouton, C. H. L.; Ferreira, D. Tetrahedron 1991, 47, 6705±6716.