Diazomethane → Methyl 11-hydroxy-4-oxotetradecanoate

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Reaction Steps

In order to determine the stereochemistry at the 11-position, 1 was hydrolyzed first with base and then with acid to yield 11-hydroxy-4-oxo-tetradecanoic acid (8). The long chain fatty acid (8) was reacted with excess diazomethane to furnish 11-hydroxy-4-oxo-tetradecanoic acid methyl ester (9). Compound 9 was converted to the two Mosher esters 10 and 11 with (R)- and (S)-methoxyphenylacetic acid (MPA), using the EDCI/DMAP coupling conditions. (Seco, J. M.; Quinoa, E.; Riguera, R., Tetrahedron: Asymmetry 2001, 12, 2915-2925.) The resulting 11-MPA esters 10 and 11 were subjected to NMR analysis. The chemical shift differences ΔδRS were significant (Scheme 1), which made it possible to conclude that 1 had the (S)-configuration at C-11. The sugars were determined as D-glucose and D-fucose by hydrolysis and determination of the sign of rotation of the isolated carbohydrates. This conclusion was supported by MM2 calculations, which indicated that only the diastereomer with both D-sugars would give the relatively strong ROESY correlations between H-11 and H—F-1 and between H—F-2 and H-G-1 that were exhibited in the spectrum of 1.

Provenance & Evidence