Revised Synthesis of 3‐O‐Cinnamyl‐, 3‐O‐p.Coumaryl‐and 3‐O‐Isoferulyl‐D‐(‐)‐Quinic Acid

Pooter, H. De; Brucker, J. De; Sumere, C. F. Van

doi:10.1002/bscb.19750840805

Cited by 12 publications

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Synthesis of 3‐0‐o.coumaryl‐, 4‐0‐o.coumaryl‐and 3‐0‐ferulyl‐d‐(‐)‐quinic acid. Improved synthesis of 3‐0‐sinapyl‐d‐(‐)‐quinic acid

Pooter¹,

Brucker²,

Sumere³

1976

Bulletin des Soc Chimique

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The title compounds were obtained by a reaction sequence starting from diphenylmethyl 4,5-0-isopropylidenequina$e. Suitably protected cinnamyl chlorides were condensed with this compound, followed by reaction of the intermediate esters with hydrazine hydrate, and then with acetic acid-formic acid-water. The total yields of 3-0-o. As already mentioned in the foregoing paper ( 5 ) . the synthesis of the title compounds by the method proposed by HASLAM et a2 for the synthesis of e.g. 3-O-p.coumaryl-D-(-)-quinicacid (1x)(6), gave rather disheartening results. In fact, the final removal of the protective functions from the easily prepared intermediates (e.g. V I ) required prolonged acidic treatment, entailing heavy losses of material. However, a s this requirement could be explained by the high stability of the employed 1-0-ethoxycarbonyl-protection (as in VI) in acidic medium, it seemed worthwhile to investigate a synthetic procedure based on the use of diphenylmethyl 4,5-0-isopropylidenequinate (II), a compound without any protection on the 1-hydroxyl-function. This approach looked promising, because in I1 a marked difference towards acid chlorides between the sterically hindered, axial tert. alcohol group on C-1 and the equatorial sec. alcohol group on C-3 may be expected (see e.g. ( 7 -1 0 ) ) .The results obtained confirm the validity of this supposition. The procedure, followed for the synthesis of the title compounds VIII, XI and XI1 is depicted in the scheme.-663 -

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