Erprobte synthese von 2-azido-2-desoxy-d-mannose und 2-azido-2-desoxy-d-mannuronsäure als baustein zum aufbau von bakterien-polysaccharid-sequenzen

Addition of Heteroatom Radicals to endo-Glycals †

“…The azidonitration of glycals was later extended to tri-O-acetyl-d-glucal (2a), but with lower stereoselectivity because not all substituents shield the same face. Furthermore, Paulsen [42] and Schmidt [43] found with this glucal 2a different selectivities depending on the reaction conditions and temperature. However, up to now the azidonitration of glycals has been the best method to synthesize 2-amino sugars by simple reduction of the azide group, and has found many applications in carbohydrate chemistry, like in a very recent synthesis of a bisphosphorylated trisaccharide [44].…”

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars

“…H 2 / Pd in dioxane/water,30 and H 2 /Pd in MeOH/H 2 O,240,241 along with the chemoselective N-deprotection reported by Hasegawa et al242 using H 2 /Pd in the presence of MeOH, HBr, and dioxane. The efficacy of these glycosyl donors has been demonstrated in the synthesis of nucleosides243 inner core of lipopolysaccharides,244 heparin derivatives, 240,245-247 dibekacin,248 Lipid A derivatives,249 glycosidic lignan variants,250 neoglycoconjugates,227 solid-phase peptide synthesis,231 and antibacterial amino glycosides, 251 among others.Versatile applications of the allyloxycarbamoyl (Alloc) protective group 252,253 prompted Boullanger et al to investigate its participating properties in 1,2-trans glycosylation reactions 254.…”

“…27 Differently, for the arabino-glycal 5 ('glucal'), mixtures of 2-azido-2-deoxy-D D-gluco 6 28 and D D-manno derivatives 7 result (Scheme 3b). 20,29,30 This higher regioselectivity can be explained by the increased steric hindrance of the top face of the D D-galactal derivative 3 in comparison to that of the D D-glucal derivative 5.…”

“…30,218,[227][228][229][230] Tetraacetate 101 can be easily prepared from either unprotected glucosamine 226 or from 2-amino tetraacetate 75a. 218 The latter approach is preferred if the synthesis of 101 in anomerically pure b-form is required (Scheme 19).…”

2,3,4-Triacetoxy-1-[5-(1,2,3,4-tetraacetoxybutyl)pyrazin-2-yl]butyl acetate

“…For general background, see: Vasella et al (1991); Alper et al (1996). For related literature, see: Bovin et al (1981); Paulsen & Stenzel (1978); Paulsen et al (1985); Pavliak & Kovac (1991). For related structures, see: Klein et al (1999); Myers et al (2000), found in a search of the Cambridge Structural Database (Version 5.28;Allen;2002).…”