Macrophages express a mannose/N-acetylglucosamine-specific lectin which serves as a receptor for nonopsonic phagocytosis of mannose-coated particles. We have examined the binding to guinea pig alveolar macrophages in a serum-free medium of 16 KlebsieUa pneumoniae serotypes and of the capsular polysaccharides isolated from 7 of these serotypes. Only five polysaccharides containing the repeating sequence Mana2/ 3Man or L-Rhaa2/3-L-Rha bound to the macrophages. Of the 11 bacterial serotypes expressing such disaccharides in their capsular polysaccharides, 7 bound efficiently, 2 bound poorly, and 2 did not bind at all. No binding occurred with five serotypes lacking these disaccharides. Binding of the bacteria was inhibited by homologous and heterologous capsular polysaccharides that contain the disaccharide sequences, by mannan, and by (Man)25BSA (where BSA is bovine serum albumin). Mana2/3Man-containing oligosaccharides were potent inhibitors compared with monosaccharides. Binding was dependent on Ca2+, modulated by cultivating the macrophages on mannan-coated surfaces, and increased in human monocyte-derived macrophages compared with monocytes. The bulk of the bacteria bound to the macrophages was internalized and killed. The data taken together suggest that Klebsiella pneumoniae cells undergo lectinophagocytosis mediated by capsular disaccharides recognized by the mannose/N-acetylglucosamine-specific lectin of macrophages. This may enhance clearance of the organisms from the serum-poor environment of the lung.

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4-0-(P-D-Glucopyranosyl)-L-rhamnose (scillabiose) has been synthesized in 55% y~eld by condensation of 2,3,4,6-tetra-0-acetyl-a-D-glucopyranosyl bromide with methyl 2.3-0-isopropylidene-a-L-rhamnopyranoside using mercuric cyanide in acetonitrile (Helferich reaction). The disaccharide and the derived alditol are both syrups but each forms a crystalline peracetate. A convenient synthesis of I-deoxy-D-erythritol is described.4-0-(P-D-Glucopyrannosyle)-L-rhamnose (scillabiose) a ete synthetise avec un rendement de 55% par reaction du a-D-tetracetylbromoglucose avec le methyl 2,3-0-isopropylidene-a-L-rhamnopyrannoside en utilisant le cyanure de mercure dans I'acetonitrile (reaction de Helferich). Le disaccharide et I'alditol correspondant son; sirops mais chacun donne un peracetate crystallin. Une nouvelle synthtse de 1-deoxy-D-erythritol est decrite.Canadian Journal of Chemistry, 50. 3373 (1972) L-Rhamnose is widely distributed in nature and is commonly found as a constituent of plant gums (I), plant glycosides (2), and in bacterial polysaccharides (3). Despite this, no disaccharide having L-rhamnose as the aglycone has been synthesized (4) with the exception of. Such disaccharides are invaluable not only for the identification of fragments obtained in structural studies but also for the determination of immunodominant groups in polysaccharides which have antigenic activity (6). The aldobiouronic acid 4-0-(8-D-glucopyranosyluronic acid)-L-rhamnose has been isolated from hydrolyzates of Acrosiphonia centralis (7), Ulva lactuca (8), and Klebsiella K9 capsular polysaccharide (9). In the first two cases this acid has been characterized after reduction to the neutral disaccharide.The synthesis of 4-0-(8-D-glucopyranosy1)-Lrhamnose (scillabiose) described here was originally undertaken mainly as a model study for the subsequent synthesis of the D-manno-analog (3) but since the related aldobiouronic acid has now been identified as a component of Klebsiella type K9 capsular polysaccharide the preparation of this disaccharide is related to our studies on these bacteria. Scillabiose was first isolated from the glycosides scillarin A and glucoscilliphaeoside obtained from Scilla maritima (2, 10) and its identification as 4-0-(P-D-glucopyranosy1)-L-rhamnose was subsequently established (1 1, 12).Methyl 2,3-0-isopropylidene-a-L-rhamnopyranoside (3) was prepared most conveniently from methyl a-L-rhamnopyranoside (1) by reaction with acetone in the presence of cation exchange resin (1 3-16) and was purified through the crystalline 4-acetate (2). Condensation of this intermediate with 2,3,4,6-tetra-0-acetyl-cr-D-glucopyranosyl bromide using mercuric cyanide in acetonitrile (17) gave methyl 4-0-(2,3,4,6-tetra-0-acetyl-p-D-glucopyranosy1)-2,3-0-isopropylidene-a-L-rhamnopyranoside (5) as a crystalline product (yield 80%).Initial attempts to prepare scillabiose heptaacetate (7) by direct acetolysis of 5 under several different conditions gave only very poor yields (1 573 of 7. This was eventually explained by the fact that direct a...

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