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Configuration of Heptopyranoside and Heptofuranoside Side Chains



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CHIRALITY 9 699 712 1997 Configuration of Heptopyranoside and Heptofuranoside Side Chains 2 Anthroate a Powerful Chromophore for Exciton Coupled CD IRINI AKRITOPOULOU ZANZE 1 KOJI NAKANISHI 1 HALSZKA STEPOWSKA 2 BARBARA GRZESZCZYK 2 ALEKSANDER ZAMOJSKI 2 AND NINA BEROVA1 1 Department of Chemistry Columbia University New York New York 2 Institute of Organic Chemistry Polish Academy of Sciences Warsaw Poland ABSTRACT The absolute configuration of the acyclic side chain of heptopyranosides and heptofuranosides was determined by exciton coupled CD employing the strongly fluorescent 2 anthroate chromophore The usage of this chromophore offers significant improvements over previous chemical and spectroscopic procedures since its intense fluorescence greatly facilitates the isolation and HPLC purification at the nanogram scale The large amplitudes of the bisignate spectra allow CD manipulations in the 1 10 7 M range Chirality 9 699 712 1997 1997 Wiley Liss Inc KEY WORDS bacterial lipopolysaccharides bichromophoric acyclic polyols 2anthroate heptose side chains Heptopyranosides of the L glycero D manno and more rarely the D glycero D manno configurations compounds 1 and 2 respectively Fig 1 exist in the inner core of bacterial lipopolysaccharides of Gram negative bacteria usually in the form of di or tri heptosides 1 It is suspected that heptofuranosides such as L glycero D mannoheptofuranose 3 might also constitute a portion of the bacterial lipopolysaccharide inner core 2 The role of these compounds is under investigation and many synthetic studies aim to create reference libraries for comparisons with authentic samples as well as for immunological studies It is expected that immunology will clarify the function of heptoses in the lipopolysaccharide system Heptopyranosides and heptofuranosides contain acyclic side chains with stereogenic centers thus representing a challenge for assignment of absolute configurations So far structural determination studies on this class of



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