1,3-Propanediol methodology

Mathieu-Pelta, I. and Evans, S.A., Highly regioselective and stereospecific functionalization of 1,2-propanediol with trimethyl(X)silanes employing the l,3,2 5-dioxaphospholane methodology, Phosph., Sulf. Silic., 75, 23, 1993. 

Recently, a series of studies of the stereoselective reduction of 1,3-diketones has been reported which expands upon this methodology. When 1,3-diphenyl-1,3-propanedione was reduced with three equivalents of NaBH4 in the presence of (S,S)-15,THFA,and ethanol in CHCI3 at -20°C, (S,S)- 1,3-diphenyl- 1,3-propanediol was obtained quantitatively in 97% ee (Scheme 9) [54], The anti syn ratio of the product was 84 16. Diketones with electron-donating and electron-withdrawing substituents on their phenyl rings were also reduced with high enanti-oselectivity and diastereoselectivity. 

The 1,3-propanediol ester, thus prepared, was transformed readily into 7-(3, 4 -methylenedioxyphenyl)-6 -heptenal, and the latter homologated by Wadsworth-Emmons reaction with the ylid of triethyl-4-phosphonocrotonate to afford ethyl 11-(3, 4 -methylenedioxyphenyl)-2E,4E, 0E undecatrienoate. The latter was simply transformed by conventional methodology into the corresponding i-butylamide, pipercide. 

Thus, the ester derived from the Lewis acid-catalyzed condensation-fragmentation sequence involving piperonal, cyclopentanone and 1,3-propanediol was readily converted to ethyl 9-(3, 4 -methylenedioxyphenyl)-non-8 -en-2-ynoate by conventional methodology (Scheme 18). This 2-alkynyl ester was then isomerized to the corresponding 2,4-dienoate by the triphenylphosphine-catalyzed internal redox process [35,136]. The 2E,4E- dienoic acid ester served as the immediate precursor of retrofractamide, 50(n=2), the P. nigrum amide 51(n=2), and dehydropipemonaline, 52, all prepared in better than 20% overall yields from piperonal (Scheme 18) [35]. 

Oh, B.R., Seo, J.W., Choi, M.H., and Kim, C.H. (2008) Optimization of culture conditions for 1, 3-propanediol production from crude glycerol by Klebsiella pneumoniae using response surface methodology. Biotechnol. Bioprocess Eng., 13 (6), 666-670. 

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