13176-47-1Relevant academic research and scientific papers
Silyl enol ethers as new protecting groups for alkyl 4-halo-3-oxobutanoates; the preparation of pure (3-alkoxycarbonyl-2-oxopropyl)triphenylphosphonium salts
Moorhoff, Cornelis M.
, p. 1987 - 1995 (2007/10/03)
A new method has been developed for the preparation of pure (3-alkoxycarbonyl-2-oxopropyl)triphenyl-phosphonium salts 8. Alkyl 4-bromo-3-oxobutanoates and alkyl 4-chloro-3-oxobutanoates 7 are protected as the trimethylsilyl enol ethers prior to treatment of the resulting bromo(trimethylsilyl enol ether) esters 20c and 21c with triphenylphosphine in toluene and then addition of a little water to give pure (3-isopropoxycarbonyl-2-oxopropyl)triphenylphosphonium bromide 8c. Bromo(silyl enol ether) esters react more efficiently with triphenylphosphine than the chloro(silyl enol ether) esters. tert-Butyldimethylsilyl enol ethers of alkyl 4-bromo-3-oxobutanoates and alkyl 4-chloro-3-oxobutanoates 7 also react with triphenylphosphine. Protection of isopropyl 4-bromo-3-oxobutanoate 7c as the enol acetate followed by subsequent reaction with triphenylphosphine gives (Z)-(2-acetoxy-3-isopropoxycarbonylbut-2-enyl)triphenylphosphonium bromide 17.
SNTHESIS AND "ANOMERIZATION" OF C-GLYCOSYL COMPUNDS RELATED TO SOME HETEROCYCLIC NATURAL PRODUCTS
Sun, King Mo,Dawe, Robert D.,Fraser-Reid, Bert
, p. 35 - 48 (2007/10/02)
Reaction of 2,3-O-isopropylidene-D-ribofuranose (13) with the stabilized Wittig reagents Ph3P=C(Me)CO2Me (14) and Ph3P=C(Me)CN (15) gave olefinic products which, upon treatment with dilute base, afforded the corresponding anhydro sugars having the β-D-anomer configuration excusively.Treatment of these kinetic products with a strong base did not affect the ester obtained from 14, but the nitrile from 15 gave a β-to-α-anomer ratio at equilibrium of 4:1.Reaction of 13 with Ph3P=CHCOMe led directly to a 7:3 mixture of β- and α-D anomers, and this ratio was changed to 1:4 upon prolonged exposure to base.Treatment of 4,6-O-ethylidene-D-glucopyranose with the Wittig reagent Ph3P=CHCOCH2CO2Et led directly to a 1:1 mixture of the anomers of the anhydro sugar in which a β-keto ester residue is attached at the (original) anomeric center.This ratio of anomeric forms coud not be changed by treatment with base, but the ethylidene-protecting group could be removed, and the resulting tetrol tritylated at the primary position.
