Total syntheses of (+)-castanospermine, (+)-epicastanospermine, their analogs, (-)-N-acetyl slaframine and (-)-N-acetyl neuraminic acid = (+)-카스타노스퍼민, (+)-에피카스타노스퍼민, 그 유도체들, (-)-엔 아세틸 슬라프라민과 (-)-엔 아세틸 뉴라민산 의 전합성

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Total syntheses of (+)-castanospermin 1, (+)6-epicastanospermin 2 and (-)-N-acethylneuraminic acid were accomplished via the stereoselective phenylselenoamidation of trichloroacetimidate derived from 172, and the asymmetric dihydroxylation of transolefins 188, 197 and 226 to produce the vicinal diols 189a and 226 as the key intermediates. Hydrogenation of 189a and the subsequent cyclization gave (+)-6-epicastanospermine 2. Two hydroxyl group of cbz-protected trihydroxy pyrrolidine 198a was chemoselectively protected, two remaining hydroxyl group was mesylated and then desilylated to furnish eposide 202, whcih was hydrogenated, cyclized and hydrolyzed sequentially to afford (+)-castanospermine 1. For (-)-N-acetylneuraminic acid, 218 was converted into triacetonide and then desilylated to provide alcohol 228. The alcohol was oxidized and reacted with vinyl magnesium bromide to give vinyl compound 230. After its oxidation to vinyl ketone 231, it was oxidatively cleaved to produce keto acid 232. Finally it was cyclized with 6N HCI to produce (-)-N-acetyl neuraminic acid 101. Regio-and stereoselective cyclization of broimdate 172 was achieved with iodine monobromide to give oxazoline imidate 203. Hydrolysis of 203 afforded diol amide 204. The intramolecular cyclization of 204 was accomplished under Mitsunobu conditions to afford pyrrolidine 205. Treatment of 205 with aqueous acid followed by protection with CBzCI to give 206. 206 was sulfonated, hydrogenated and then cycized to produce (+)-7-deoxy-6-epicastanospermine 3. Alternatively oxazoline imidate 203 was hydrolyzed and protected as benzyl carbamate to furnish benzyl carbamate 213. Reduction of 213 provided tetraol 214. 214 was converted into (+)-7,8-dideoxy-6-epicastanospermine 4 by the described sequence for 3. Ring opening of 218 followed by esterification and the ensuing lithium borohydride reduction produced alcohol 219. 219 was converted into phosphonium salt 220, and then olefinated with aldehyde 116a. ...
Kang, Sung-Horesearcher강성호researcher
한국과학기술원 : 화학과,
Issue Date
144205/325007 / 000945107

학위논문(박사) - 한국과학기술원 : 화학과, 1998.8, [ iii, [116] p. ]

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