- Synthesis of trisaccharides by hetero-diels-alder welding of two monosaccharide units
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A new strategy for the synthesis of di- and trisaccharides based on the de novo synthesis of the linking saccharide unit is presented. In this strategy, functionalized monosaccharide building blocks already incorporating the glycosidic linkages are welded together using a metal-catalyzed hetero-Diels-Alder (HDA) reaction to generate a new monosaccharide unit between them. The highest yields and selectivities in the HDA reaction were obtained by using chiral Schiff base chromium complexes. Disaccharide products were accessible by reaction of Danishefsky's diene with acetyl- and benzyl-protected galactoside aldehydes. For the synthesis of trisaccharide products, acetyl-protected glucose or galactose-derived dienes were fused with monosaccharide-derived aldehydes using chromium catalysts for the HDA reaction. The desired trisaccharide products were obtained in moderate to good yields with excellent stereoselectivity. The central pyranulose-ring generated in the process possessed an L-cis-enulose configuration according to NMR spectroscopy and modeling studies. 1 + 1 equals 3! The hetero-Diels-Alder union of two functionalized monosaccharide building blocks - one bearing an aldehyde and the other a readily accessible diene moiety - affords functionalized trisaccharide structures in moderate to good yields and excellent stereoselectivities when β-anomers of the aldehydes are used. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
- Himanen, Jatta A.,Pihko, Petri M.
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supporting information; experimental part
p. 3765 - 3780
(2012/09/25)
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- Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica
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A series of methoxy and deoxy derivatives of mannopyranose-1-phosphate (Manp-1P) were chemically synthesized, and their ability to be converted into the corresponding guanosine diphosphate mannopyranose (GDP-Manp) analogues by a pyrophosphorylase (GDP-ManPP) from Salmonella enterica was studied. Evaluation of methoxy analogues demonstrated that GDP-ManPP is intolerant of bulky substituents at the C-2, C-3, and C-4 positions, in turn suggesting that these positions are buried inside the enzyme active site. Additionally, both the 6-methoxy and 6-deoxy Manp-1P derivatives are good or moderate substrates for GDP-ManPP, thus indicating that the C-6 hydroxy group of the Manp-1P substrate is not required for binding to the enzyme. When taken into consideration with other previously published work, it appears that this enzyme has potential utility for the chemoenzymatic synthesis of GDP-Manp analogues, which are useful probes for studying enzymes that employ this sugar nucleotide as a substrate.
- Zou, Lu,Zheng, Ruixiang Blake,Lowary, Todd L.
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p. 1219 - 1226
(2012/09/21)
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- Synthesis of monomethyl derivatives of p-nitrophenyl α-d-gluco, galacto, and mannopyranosides and their hydrolytic properties against α-glycosidases
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All possible monomethyl derivatives of p-nitrophenyl α-D-gluco, galacto, and mannopyranosides were synthesized. Hydrolytic activities of α-glucosidase (rice), α-galactosidases (green coffee bean, Mortierella vinacea, and Aspergillus niger), and α-mannosidases (almond and jack bean) against them were elucidated. The 6-O-methyl galactopyranoside and mannopyranoside were hydrolyzed by the M. vinacea α-galactosidase and the almond and jack bean α-mannosidases, respectively, while these enzymes did not act on the 2-, 3-, and 4-O-methyl derivatives. On the other hand, rice α-glucosidase and green coffee bean and A. niger α-galactosidases had no hydrolyzing activities at all against the respective four monomethylated substrates.
- Hakamata, Wataru,Nishio, Toshiyuki,Sato, Reiko,Mochizuki, Takahiro,Tsuchiya, Kazuya,Yasuda, Maki,Oku, Tadatake
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p. 359 - 377
(2007/10/03)
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