Halogeno-esters

Secondary halogen esters are also known. The addition of bromine to D-glucal 3,4,6-triacetate (p. 401) produces 3,4,6-tri-0-acetyl-2-bromo-2-deoxy-D-glucopyranosyl bromide (14 ). Methyl 4,6-dichloro-4,6-dideoxy-ct-D-glucopyranoside 2,3-sulfate was obtained by the action of sulfuryl chloride on methyl a-D-glucopyranoside 150), 

Helferich and Gnuchtel 114) state that iodide replacement by the action of sodium iodide in acetone is not confined exclusively to the 6-0-mesyl group but also took place with an 0-mesyl group substituted at carbon 4. 

The naturally occurring phosphate esters are products of intermediary metabolism and are of great metabolic importance (Chapter XIII). They 

Dissociation Constants of Some Sugar Phosphates [Compiled by L. F. Leloir (151)] 

The phosphoric mono- and diesters of the sugars are strongly acidic substances isolated often as crystalline barium, calcium, lead, sodium, cyclo-hexylammonium, or alkaloid salts. They are usually stronger acids than free orthophosphoric acid (Table II), a fact which has been rationalized according to modern theory (152). 

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Note Aminolysis of halogeno esters may be accompanied by amide formation, depending on the amine and conditions employed. 

Dihydrothieno[3,4-d]pyrimidines 364 were JV-alkylated at position 3 with a variety of a-halogeno esters in the presence of base [81JAP(K)104870]. 

As happens with comparable arsenic compounds, some a-halogeno esters and amides react with oxo compounds in the presence of stibines, but without the need of base, to form... 

Palladium(II)-catalysed cross-coupling reactions involving stan-nanes have continued to be developed, a-Halogeno-esters and -lactones couple with allylstannanes and a-stannyl-ketones in good... 

The iV-phosphorylated ketenimines (293), obtained by the action of trialkyl phosphites on a-cyano-a-halogeno-esters, are converted by the action of nucleophiles into phosphoramides (294). According to the nature of... 

Synthesis.— The preparation of a-amino-acids from a-halogeno-acids and ammonia is often unsatisfactory owing to the occurrence of multiple alkylations etc. A way around this problem is to treat a-halogeno-esters with alkali-metal cyanates and an alcohol this gives N-alkoxycarbonyl-a-amino-esters in >90% yield. " The O-arylhydroxylamine (148) is a useful reagent for aminating enolates, especially those derived from malonic esters, which can thus be... 

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