[reaction: see text] Direct synthetic access to glycosyl-1-phosphates is accomplished with the dehydrative coupling of carbohydrate hemiacetals and dialkyl phosphates, employing dibenzothiophene-5-oxide and triflic anhydride. The procedure offers a new and versatile method for efficient preparation of a host of glycosyl-1-phosphates of variable structure with good control over anomeric selectivity.
Recent advances in peroxidase-mediated biotin tyramide (BT) signal amplification technology have resulted in high-resolution and subcellular compartment-specific mapping of protein and RNA localization. Horseradish peroxidase (HRP) in the presence of H 2 O 2 is known to activate phenolic compounds for phenoxy radical reaction with nucleic acids, where biotinylation by BT is a practical example. BT reactivity with RNA and DNA is not understood in detail. We report that BT phenoxy radicals react in a sequence-independent manner with guanosine bases in RNA. In contrast, DNA reactivity with BT cannot be detected by our methods under the same conditions. Remarkably, we show that fluorescein conjugates DNA rapidly and selectively reacts with BT phenoxy radicals, allowing convenient and practical biotinylation of DNA on fluorescein with retention of fluorescence.
Synthesis of Glycosyl-1-phosphates via Dehydrative Glycosylation.Page 2135. A key reference for glycosyl phosphate synthesis employing glycosyl pyridyloxy donors by Hanessian and coworkers was inadvertently overlooked: Hanessian, S.; Lu, P.-P.; Ishida, H.
Dehydrative Glycosylation with Activated Diphenyl Sulfonium Reagents. Scope, Mode of C(1)-Hemiacetal Activation, and Detection of Reactive Glycosyl Intermediates.-Several 1-hydroxyglycosyl donors are glycosylated by a new one-pot method employing the reagent combination of Ph 2 SO and Tf 2 O to activate the starting donor. The following addition of the nucleophilic acceptor is accomplished in the presence of 2-chloropyridine as an inexpensive triflic acid scavenger. A wide variety of glycosyl acceptors, including primary, secondary, and tertiary alcohols, as well as phenols, electron-rich C-aryl nucleophiles, N-silyl amides, N-silyl pyrimidine, azide, and carboxylic acids are compatible with this dehydrative glycosylation procedure. It is worth noting that extremely hindered nucleophiles such as tert-butyl alcohol give good yields, and free N-H of carbamate functionalities are tolerated. Several experiments are made to establish the mechanism of the method. -(GARCIA, BRIAN A.; GIN, DAVID Y.; J.
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