Hiroshi Kawakami

Sialic Acid in Human Milk: Composition and Functions

Breast milk is the best nutrient source for infants. It contains all elements needed for a normal growth and development of infants. Human milk contains a large amount of sialic acid compared with bovine milk. Sialic acid contained in oligosaccharides, glycolipids and glycoproteins in milk is considered to play important roles in physiological functions in infancy. Thus, we have investigated the sialic acid composition and the functions of sialylated compounds in human milk. Sialic acids comprise a family of neuraminic acid derivatives present in secretions, fluids and tissues of mammals. In milk, sialic acid is present in different sialoglycoconjugate compounds such as oligosaccharides, glycolipids and glycoproteins, not in a free form. Human milk contains 0.3-1.5 mg/ml of sialic acid. Sialic acid bound to oligosaccharides accounts for about 75% of the total sialic acid contained in human milk. Most of the sialic acid contained in human milk is found in the form of sialyllactose, an oligosaccharide formed from lactose and sialic acid. In milk, gangliosides, sialic acid-containing glycolipid, occur mainly as monosialoganglioside 3 (GM3) and disialoganglioside 3 (GD3). The concentration of GM3 in human milk increases, while that of GD3 concentration decreases during lactation. Because the brain and central nervous system contain considerable level of sialic acid in infancy, it is considered to play important roles on the expression and development of their functions. Moreover, we found that some sialylated compounds had inhibited the adhesion of toxins, bacteria and viruses to the receptors on the surface of epithelial cells. Additionally, we found that some sialylated compounds had growth-promoting effects on bifidobacteria and lactobacilli, predominantly present in the intestinal flora of infants fed with human milk. The results suggested that sialylated compounds in human milk possibly behaved as a physiological component in the intestinal tract of infants to protect them against enteric infections.

Synthesis of (+)-trans-Whisky Lactone, (+)-trans-Cognac Lactone and (+)-Eldanolide

A new and useful synthesis of (+)-trans-whisky lactone (3), (+)-trans-cognac lactone (4) and (+)-eldanolide (5) starting from levoglucosenone (1) is described

Synthesis of (+)-trans-whisky lactone, (-)-cis-whisky lactone, (+)-cognac lactone and (+)-eldanolide

(+)-trans-Whisky lactone (5) and (-)-cis-whisky lactone (8), (+)-cognac lactone (9) and (+)-eldanolide (10) were synthesized starting from levoglucosenone (1) in optically pure states

Stereoselectivities in the coupling reaction between silytated pyrimidine bases and 1-halo-2,3-dideoxyribose

Coupling reactions between 1-chloro-2,3-dideoxyribose and silylated pyrimidines have been examined from the point of stereoselectivity. When the reaction was carried out in chloroform, the selectivity was in the anomeric ratio of α:β=4:6. On the other hand, the presence of tertiary amine raises the selectivity to α:β=3:7

Synthesis of sex pheromones of the Japanese Beetle and Cupreus Chafer Beetle

The pheromones (1a,1b) of two insect pests, the Japanese Beetle (Popillia japonica, Newman) and Cupreus Chafer Beetle (Anomala cuprea, Hope), were synthesized. Starting from protected D-Ribose, 1a was prepared in 8 steps with a 30% total yield. The same chemistry was demonstrated for the synthesis of 1b.

Nucleoside synthesis from furanoid glycals

Reaction of furanoid glycals with PhSCl afforded 1-chlorosugars, which were used for condensation reaction with silylated uracil in the presence of SnCl4. These two reactions proceeded in a highly stereoselective manner

Synthesis of 1,6:3,4-Dianhydro-b-D-talopyranose from Levoglucosenone: Epoxidation of Olefin via trans-Iodoacetoxylation

Levoglucosenone (1,6-anhydro-3,4-dideoxy-β-D-glycero-hex-3-enopyranos-2-ulose, 1) was converted to give 1,6:3,4-dianhydro-β-D-talopyranose (8) in good yield through stereoselective trans-iodoacetoxylation followed by basic hydrolysis

The synthesis of 2'-deoxy-5-trifluoromethyluridine utilizing a coupling reaction

The coupling reaction between 1-α-chloro-2-deoxyribose derivative and silylated 5-trifluoromethyluracil was examined. The best stereoselectivity was obtained when the reaction was carried out using a large amount of silylated base in the presence of anhydrous zinc chloride

Wittig-Horner reaction of dimethyl phthalide-3-phosphonates with aldehydes: synthesis of 3-ylidenephthalides and characterization of their E- and Z-isomers

Wittig-Horner reaction of dimethyl phthalide-3-phosphonates with aldehydes in the presence of lithium bis(trimethylsilyl)amide was investigated. Using their NOE experiments, both the E- and Z-isomers of 3-ylidenephthalides were clearly characterized

Condensation Reaction Between 2,2-Diphenylthio-2,3-Dideoxyribose and Silylated Pyrimidine Bases

Abstract The condensation reaction between 2,2-diphenylthio-2,3-dideoxyribose and silylated pyrimidine bases was examined. In the presence of TMSOTf as a catalyst, this reaction proceeded to give the nucleosides in the ratio of α: β = 2:8. Each β-anomer was converted to protected 2′,3′-dideoxynucleosides.