Maltose type

Syntheses of the maltose-type trehazolin derivatives 448 and 451 from D-galactose have been reported (Schemes 65 and 66).51 These were expected to manifest specific inhibitory activity toward maltases. Coupling of 26 with 5 gave the thiourea derivative 446, whose treatment with 2-chloro-3-ethylbenzoxazolium tetrafluoroborate and Et3N, afforded the aminooxazoline derivative 447. Subsequent hydrogenolysis of 447 furnished 448. 

Acarviosin 441, an a-glycosidase inhibitor, is a maltose-type pseudodisaccharide that can be prepared from methanolysis of acarbose 442 [255]. It has been shown to have five times more inhibitory activity than its precursor acarbose, for which the first total synthesis has been described by Ogawa s group in 1989 [256]. 

In addition, the corresponding isomers with the a-glycosidic linkage are possible. The free hydroxyl group of the hemiacetal of a disaccharide cannot be assigned to a configuration the a- and /3-form are in equilibrium. The first two disaccharides listed are of the trehalose type the rest, of the maltose type. 

Disaccharides of the Maltose Type. Maltose (4-a-glucopyranosido-glucose) is a product of the breakdown of starch and occurs in malt (malt sugar). As we have mentioned, it is reducing. 

In the confectionery industry, com symps are used extensively in nearly every type of confection, ranging from hard candy to marshmallows. In hard candies, which are essentially soHd solutions of nearly pure carbohydrates, com symp contributes resistance to heat discoloration, prevents sucrose crystallization, and controls hygroscopicity, viscosity, texture, and sweetness. Maltose symps, high conversion symps, and acid-converted symps (36 and 42 DE) are used for this appHcation. 

The separation was carried out on a TSKgel Amide-80 column 4.6 mm i.d. and 25 cm long with a mobile phase consisting of a 80% acetonitrile 20% water mixture. The flow rate was 1 ml/min and the column was operated at an elevated temperature of 80°C. The saccharides shown were 1/ rhamnose, 2/ fucose, 3/ xylose, 4/ fructose, 5/ mannose, 6/ glucose, 7/ sucrose and 8/ maltose. The analysis was completed in less than 20 minutes. These types of separations including other biomonomers, dimers and polymers are frequently carried out employing refractive index detection. 

An early report from Shukla et al.129 showed efficient hydrolysis and isomerization reactions of disaccharides, including cellobiose, maltose, and lactose, over zeolites type A, X, and Y. Abbadi et al.130 studied the hydrolysis of maltose, amylose, and starch over the zeolitic materials H-mordenite, H-beta, and mesoporous MCM-41. The effect of temperature and pressure, as well as that of the Si/Al ratio of H-mordenite and H-beta zeolites, on their catalytic activity was investigated for the... 

The best-studied systems to date are those for the uptake of maltose, histidine, siderophores and vitamin B12. Typical of all the ABC-type importers are the soluble binding proteins, which bind the substrate with high affinity. Early studies revealed that many binding proteins could be extracted from Gramnegative bacteria by an osmotic shock procedure, giving rise to the term osmotic-shock-sensitive transport systems. It still holds true that the majority... 

Kobe B, Center RJ, Kemp BE, Poumbouris P. 1999. Crystal structure of human T cell leukemia virus type 1 gp21 ectodomain crystallized as a maltose binding protein chimera reveals structural evolution of retroviral transmembrane proteins. Proc Natl Acad Sci USA 96 4319-4324. 

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