A re-examination of the reactions of (Z)-2,3:5,6-bis-O-(1-methylethylidene)-N-(phenylmethylidene)-$\alpha$- scD-mannofuranosylamine N-oxide and (Z)-2,3:5,6-bis-O-(1-methylethylidene)-N-(phenylmethylidene)-$\beta$- scD-gulofuranosylamine N-oxide with methylmagnesium bromide was undertaken to determine why the former gave the addition product in low yield and only moderate stereoselectivity, while the latter proceeded in high yield and with high stereoselectivity. A mechanism was proposed to explain the differences and three additional benzaldehyde nitrones bearing chiral auxiliaries derived from scD-lyxose were examined. The key interaction was indicated to be the formation of a chelated structure between the oxygen at C(5), the furanosyl oxygen and a magnesium atom. N-Glycosylnitrones that could form the chelate gave the corresponding N-hydroxy-$\alpha$-methylbenzenemethanamine after hydrolysis of the chiral auxiliary in high yield with high stereospecificity. / Pretreatment of the N-glycosylnitrones with TMSCl (2-5 equiv; 0$\sp\circ$C) prior to the addition of methylmagnesium bromide ($-$78$\sp\circ$C) afforded after hydrolysis, N-hydroxy-$\alpha$-methylbenzenemethanamine with the opposite configuration from the one in the absence of TMSCl. / In addition to benzaldehyde nitrones, N-glycosylnitrones derived from aliphatic aldehydes were shown to undergo diastereospecific addition of methylmagnesium bromide to give the corresponding N-hydroxy-$\alpha$-methylalkylamines in good yield with high ee. The absolute configuration of the product was also reversed upon pretreatment with TMSCl. / Intramolecular versions of this process were attempted. The N-methylnitrone of 3-(2-iodophenyl)propanal reacts smoothly with $\sp t$BuLi at $-$78$\sp\circ$C to give N-hydroxy-N-methyl-1-aminoindane in 92% yield. However, analogous reaction of the corresponding N-glycosylnitrone afforded the cyclic hydroxylamine in only 8.7% ee. Finally, initial attempts to achieve stereospecific carbon-carbon bond formation by radical addition to N-glycosylnitrones failed. / Source: Dissertation Abstracts International, Volume: 56-01, Section: B, page: 0247. / Major Professor: Martin A. Schwartz. / Thesis (Ph.D.)--The Florida State University, 1994.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77351 |
| Contributors | Savidakis, Michael C., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 153 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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