From methanolic extracts of fresh flowers of Primula officinalis 19 flavonoids were isolated or detected: quercetin, luteolin, kaempferol, isorhamnetin, apigenin; quercetin 3-O-glucoside, -rutinoside, -robinobioside, -gentiobioside, -(glucosyl-(1-->2) -glucosyl-(1-->6))-glucoside, -(rhamnosyl)-robinobioside; isorhamnetin 3-O-glucoside, -rutinoside, -robinobioside, -(rhamnosyl) -robinobioside; kaempferol 3-O-rutinoside, -robinobioside; limocitrin 3-O-glucoside; 3', 4'-dihydroxyflavonglucoside. Other compounds isolated were epicatechin, epigallocatechin, and proanthocyanidin B 2.

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The stereocontrol exerted by the (C0)5Cr fragment is revealed in the endo/exo ratio of (2b + 3)/2a =60/40. A similar ratio is observed for the isolobal methyl methacrylate in AICl,-catalyzed reactions; ['] however, the uncatalyzed reaction is known to satisfy poorly the Alder endo rule161 and results therefore in a reversal of the product distribution."] The olefin-carbene complex 3 belongs to a class of compounds that is important for the discussion of the mechanism of the olefin metathesis reaction.[*] To date only a few compounds containing other metals have been isolated;191 3 is the first example of a chromium compound. Complex 3 is preferentially formed in good yield by heating the mixture of isomers 2a,b and can be separated from the unchanged ex0 isomer 2a by column chromatography.The structure of 31"'1 confirms the alkene coordination of the olefin-carbene ligand to the Cr(CO), fragment, which is possible owing to the endo position of the carbene carbon atom C1 on the norbornene skeleton (Fig. 1). The alkene function is thereby bonded unsymmetrically to the metal ; the Cr-Calkene distances (2.286(3) and 2.366(3) A'' 'I) are relatively longLiZ1 Both findings are a consequence of the rigidity of the norbornene skeleton and the short separation of the chromium-coordinated carbene and alkene functions by only two carbon atoms (C31, C36). The deviation from ideal octahedral symmetry at the central metal atom is due to the chelate structure. The Cr-C1 distance of 2.017(3)A places 3 in the class of complexes with short Cr-Cc;lrbrnc

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