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Review | Special issue | Vol 79, No. 1, 2009, pp.219-228
Published online, 17th December, 2008
DOI: 10.3987/REV-08-SR(D)7
■ (-)-Indolizidine 167B via 4-Pyrrolylbutanals: Two Synthetic Methodologies at Comparison

Roberta Settambolo*

*ICCOM-CNR, Pisa Section, Department of Chemistry and Industrial Chemistry, University of Pisa, Via Risorgimento 35, 56126 Pisa, Italy

Abstract

This review relates the results that we obtained in the field of the total synthesis of (-)-indolizidine 167B, based on the intramolecular cyclodehydration of a 4-pyrrolylbutanal to a 5,6-dihydroindolizine core, according to “oxo” or “non oxo” methodology. In the former pathway the butanal was (R)-4-(pyrrol-1-yl)heptanal and originated from (R)-3-(pyrrol-1-yl)but-1-ene via rhodium-catalyzed hydroformylation. In the latter one the proper (R)-4-carboxyethyl-4-(pyrrol-1-yl)butanal intermediate was obtained from diethyl-2-(pyrrol-1-yl)pentanedioate via chemo- and regioselective reduction of the sole distal ester group. In both cases a diastereoselective hydrogenation of the final 5-n-propyl-5,6-dihydroindolizine gave the target compound.