41-thio-Maltose

In the thiomaltose series the same approach was used for the synthesis of 4,4 -dithiomaltotriosides (48a,48b) (Scheme 16) [43]. However the sequence of reactions is much longer since the -chloride intermediate (46) was formed in 83% yield only when the peracetylated /3-4-thiomaltose (45) was used, and the 1,4-dithiomaltose peracetate (47b) was obtained via the corresponding S-benz-oyl analogue (47 a). Under these conditions the 4,4 -dithiomaltotriosides were obtained in -20% overall yield from the 4-thio-/ -maltose peracetates (45). 

Reaction of peracetylated l-thio-a-o-glucopyranose (10a) with peracetylated 6-deoxy-6-iodomaltose (18), 6 -deoxy-6 -iodomaltose (21a) and 6 -deoxy-6 -iodomalto-oligosaccharides (21 b,21 c) gave the corresponding S-a-glucosylthio-maltose derivatives (20,23a-c) in excellent yields (Scheme 7) [24,28,29aj. 

Ethyl l-thio-/3-maltoside heptaaeetate (59) has proved to be a useful intermediate in the synthesis of the a-glycoside of maltose (see Section III).30 Treatment of /3-maltose octaacetate with ethanethiol and fused zinc chloride gave compound 59 in 83% yield. Synthesis of mal-... 

Growth substrate Maltose (mM) Methyl a-D-glucopyranoside (mM) Ethyl 1-thio-a-D-glucopyranoside (mM) References Comments... 

PHAs containing unsaturated or brominated side chains have been used as substrates for the production of glycoconjugates (derivatives of per-O-acetyl-l-thio-P-maltose-PHAs) via anti-Markovnikov additions. As expected, maltosyl-PHAs showed an enhanced hydrophihcity and hence better solubility and bioavailability (Constantin et al. 1999). 

Hepta-O-acetyl-a-D-lactosyl bromide, H-7 l,2,2",3,3",4",6-H ta-0-acetyl-p-maltose, M-15 l,2,2",3",4",6,6"-H ta-0-acetyl-p-maltose, M-15 l,2, 3,3",4",6,6"-H ta-0-acetyl-p-maltose, M-15 2,2, 3,3",4",6,6"-H ta-0-acetyl-p-maltose, M-15 Hepta- O -acetyl-a-primeveropyranose, X-47 Hepta-O-acetyl-p-primeveroside, X-47 Hepta-O-acetyl-p-rutinose, R-44 2,2, 3,3, 4, 6,6 -Hepta-0-acetyl-l-thio-p-E>-ceIIobiose, T-60 Hepta-O-acetyl-P-turanopyranose, T-201 Hexa-O-acety 1-1,6-anhydro-6-bromomaltose, M-15 Hexa-O-acetyl-a-robinobiosyl bromide, R-28 a-L-/Ar o-4-Hex-4-enopyranuronosyl-D-galacturonic add, H-80 Hyalbiuronic acid N-Ac, H-127... 

The discovery of the cyclic AMP receptor protein (CAP) in E. coli is most intriguing because it further illustrates the complexities of gene expression even in a relatively uncomplicated system. In E. coli, cyclic AMP stimulates the elaboration of catabolic enzymes involved in the breakdown of arabinose and maltose [184, 185]. A mutant of E. coli has been found that fails to grow on maltose and arabinose. The mutants lack a protein receptor for the cyclic AMP which is believed to bind probably to DNA, but possibly to RNA, which must be present for the induction of the catabolic enzymes. It has also been shown that in order to secure optimal transcription of the lac operon (see below), both the inducer—for example, isopropyl thio-galactoside—and cyclic AMP must be added. 

The re osdective sul tion of several mono- and di-saccharide derivatives via dibutylstannylene acetals has been investigated methyl 4,6-0-bem dene-a-D-gluco- and -galacto-pyranoside were sulfated at 0-2 in 84 and 79% yield, respectively, and />-methoxyben I 6-0-/-butyidimethyIsil34-P-D-gaIactopyranoside at 0-3 in 92% yield " phenyl l-thio-3-lactoside gave the 3 -sulftte in 76% yield, accompanied by 10% of the 3, 6 -disul te, and similar results were obtained with phenyl 2-acetamido-2-deoxy-l-thio-P-lactoside," " whereas the maltose derivative 51 reacted preferentially at 0-2. "... 

The use of 2,3,4,6-tetra-0-acetyl-5-thio-a-D-glucglycosyl donor is covered in Chapter 3. The key-steps in the syntheses of the sulfur-linked di- and trisaccharides 27 and 28 were the substitution of the triflate group of compound 26 by the anions of 1-thio-P-D-glucose and 1,4-dithio-p-cellobiose, respectively. Various photolabile (3-azibutyl)thioethers of maltose and maltotriose have been prepared by displacement of the appropriate sugar triflates by KSAc, followed by 5-deacctylation and alkylation with 3-azibutyl-l-... 

D Glucopyranosyl-D-glucitol, 45B, 470 Sophorose monohydrate, 44B, 403 Isomaltulose, 39B, 310 a-Lactose monohydrate, 37B, 244 a-Melibiose monohydrate, 42B, 323 a,p-Melibiose monohydrate, 44B, 403 -Maltose monohydrate, 35B, 266 43B, 546 2H26BrNaO,3, Sucrose-sodium bromide dihydrate, 11, 624 2H26O4S3, 2-S-Ethyl-2-thio-D-mannose diethyl dithioacetal, 40B,... 

Reactions carried out on disaccharide derivatives included the conversion of peracetates to l-phenylthio- 3-derivatives by use of phase-transfer methods and the epimerization at C-2 by calcium -amine systems (CaCl2.2H20, EtjN, for example). By this means maltose, lactose, isomaltose and melibiose were converted into the corresponding glucosyl-D-mannoses. An extensive range of variously substituted maltosyl fluorides have been made from maltose derivatives as substrates for cyclodextrin transferase. Only the 6 -methyl ether and 6 -acetate were transformed into cyclic products. In the course of the work the thio-derivatives (83) and (84) were made. ... 

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