Pyridinium chlorochromate-Hydrogen

OXIMES Hydrogen peroxide. Pyridinium chlorochromate-Hydrogen peroxide. Sodium dithionite. Vanadium(II) chloride. 

Nickel peroxide. Oxoperoxobis(N-phenylbenzohydroxamato) molyb-denum(VI). Palladium(II) acetate-Tri-phenylphosphine. Palladium /-butyl peroxide trifluoroacetate. Periodic acid. Permonophosphoric acid. Potassium dichromate. Potassium hydrogen persulfate. Pyridinium dichromate. Ruthenium tetroxide. Selenium dioxide. Sodium hypochlorite. Titanium(IlI) chlo-ride-Hydrogen peroxide. Potassium nitrodisulfonate. Potassium peroxodi-sulfate. Pyridinium chlorochromate. Pyridinium chlorochromate-Hydrogen peroxide. Sodium permanganate monohydrate. Tetra-n-Butylammonium periodate. Thailium(III) acetate. Trimethyl-amine N-oxide. Triphenylmethylphos-phonium permanganate. 

This protecting group is stable to n-BuLi (THF, — 25°C), s-BuLi (Et20, -25 °C), LDA, saturated ammonium chloride solution, water, MeOH, sodium hydrogen carbonate solution (2m), pyridinium dichromate/ dichloromethane, and, surprisingly, KF.2H20/THF/H20. It is unstable to 0.1 M HC1, 1m KOH, 75% aqueous AcOH, NaBH4, and pyridinium chlorochromate/dichloromethane. 

Hydrogenation of olefin 4, followed by 0-desilylation and 0-tosylation next procured tosylate 3, which cyclised readily when exposed to excess potassium hexamethyldisilazide. Elaboration of the ketophosphonate side chain of 20 was accomplished by condensing ester 2 with the lithiated anion of dimethyl methylphosphonate. After concurrent removal of the 1,3-dioxolane acetal and the MOM ether from 20, the resulting secondary alcohol was oxidised with pyridinium chlorochromate (PCC) to produce methyl ketone 1. 

Benzyl 3-(9-benzyl-2-deoxy-4,6-0-isopropyhdene-a,p-D-arabino-hexopyranoside (32) and methyl 3-(9-benzyl-2-deoxy-4,6-0-isopropylidene-a-D-ribohexopyranoside were prepared from D-glucose and used as precursors for the syntheses of 13 and its analogue 39, respectively (Scheme 3). The crucial step was the formation of the pyrrohdine ring in 35 from 34, which was effected by sodium borohydride reduction followed by alkaline treatment. The pyrrolidine 35 was then coupled with benzyloxycarbonyl-L-vahne via an active ester or by the DCC method to give 36, which was converted to the lactone 37 by acid hydrolysis followed by oxidation with pyridinium chlorochromate. Finally, the lactone 37 was hydrogenated to give 38, a precursor for 13. 

Synthesis from o-arabinose (35, 55 )-Quinuclidine-3,5-diol (2) has been synthesized from D-arabinose by conversion to the furanoside 21 in 59% overall yield (Schemes 4) Oxidation of the C-3 hydroxyl group with pyridinium chlorochromate followed by treatment with [(methoxycarbonyl)methylene]triphenylphosphorane and subsequent hydrogenation gave the corresponding ester, which upon reduction, mesylation and nucleophilic displacement of the mesylate group by azide ion afforded the branched azi-doethyl lyxofuranoside 22. Two pathways were used to convert 22 into 2. Acid hydrolysis of... 

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