Investigation of steric and functionality limits in the enzymatic dihydroxylation of benzoate esters. Versatile intermediates for the synthesis of pseudo-sugars, amino cyclitols, and bicyclic ring systems.
A series of benzoate esters (methyl, ethyl, n-Pr, i-Pr, n-Bu, t-Bu, allyl, and propargyl) were subjected to enzymatic dihydroxylation by E. coli JM 109(pDTG 601) strain in a whole-cell fermentation. The cis-cyclohexadienediols were obtained in yields of approximately 1g/L except for n-propyl- and i-propyl benzoate which were found to be poor substrates. n-Butyl and t-butyl benzoates were not oxidized at all. The absolute stereochemistry for all metabolites was determined by comparison with a standard prepared from (1S-cis)-3-bromo-3,5-cyclohexadiene-1,2-diol, whose absolute configuration is well established. The free diols were found to be quite stable compared to other cis-dihydrodiols of this type, however, their acetonides underwent a dimerization via a regio- and stereoselective Diels-Alder cycloaddition. The diol derived from ethyl benzoate was subjected to a stereo- and regioselective inverse electron demand Diels-Alder cycloadditions with several dienophiles. The new adducts were completely characterized. The hetero-Diels-Alder reaction of this diol with an acyl nitroso dienophile yielded regio- and stereoselectively a bicyclic oxazine, which upon reduction provided a useful derivative of amino shikimate that can be exploited in an approach to oseltamivir (Tamiflu) and other amino cyclitols. The diol was also converted to carba-alpha-L-galactopyranose to demonstrate its potential utility as a source of pseudo sugars. Experimental and spectral data are provided for all new compounds.
Fabris
Fabrizio
F
Università Ca' Foscari di Venezia, Dipartimento di Chimica, Dorsoduro 2137, I-30123, Venezia, Italy.
Collins
Jonathan
J
Sullivan
Bradford
B
Leisch
Hannes
H
Hudlicky
Tomas
T
D001565:Benzoates / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis*; D002241:Carbohydrates / Q000737:chemistry*; D054812:Cyclitols / Q000138:chemical synthesis*; D049308:Dioxygenases / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D004952:Esters / Q000737:chemistry* / Q000378:metabolism*; D005690:Galactose / Q000138:chemical synthesis; D006900:Hydroxylation; D053139:Oseltamivir / Q000138:chemical synthesis; D010084:Oxidation-Reduction; D016958:Pseudomonas putida / Q000201:enzymology; D013237:Stereoisomerism
D001565:Benzoates; D001643:Bridged Bicyclo Compounds; D002241:Carbohydrates; D054812:Cyclitols; D004952:Esters; D053139:Oseltamivir; D049308:Dioxygenases; D005690:Galactose