Synthese und Impuls‐Fourier‐Transform‐¹³C‐NMR‐Untersuchungen verzweigter Kohlenhydrate

Abstract

auf das Vorliegen des Anions von ( 5 ) hin. Dagegen geben die spektroskopischen Befunde keinen sicheren Anhaltspunkt fir eine tautomere Hydroxyform von (5).Der Saurecharakter von PCB-SH (5) wird durch die Biidung des Pyridiniumsalzes ( 3 a ) sowie die glatte uberfuhrung in den S-Methylester (6) mit Diazomethan unterstrichen. Die Umsetzung von (5) mit Phenyl-sulfenylchlorid fuhrt zum unsymmetrischen Disulfid (7).(5) -t % -Hg-S ) p 0 0 0

A concise and general entry into (R)-4-hydroxy-2-substituted cyclopent-2-enones fromD-glucose: chiral intermediates for the synthesis of PGE2, (–)-pentenomycin I, and allethrin

“…in tetrahydrofuran and hexamethylphosphoric triamide (THF-HMPT) produced alcohol (4) in 93% yield which, after treatment with mesyl chloride and triethylamine according to Crossland and Servis' method,' followed by acidic hydrolysis, gave the mesyl ester Treatment of compound (8) with 80% formic acid in THF (1 : 1) afforded an inseparable mixture of (R)-2-hydroxy-4-keto aldehyde (9) and its hydrated equivalent in 66% isolated yield. The hydrated form of compound (9) most probably adopts the more stable cyclic structure (10) as has been suggested for a similar case by M ~f f a t . ~ Assignment of structure (9) resulted from the analysis of its spectral data; of diagnostic significance were the IR absorptions at 3 400 cm-' (vOH) and 1650-1 700 cm-' (vco, vcHo); and the signal 6 9.7 (CHO) in the 'H NMR spectrum which integrated for less than one proton.…”