Expeditious asymmetric synthesis of a stereoheptad corresponding to the C(19)-C(27)-ansa chain of rifamycins: Formal total synthesis of Rifamycin S

Turks, M.Huang, X. G.Vogel, P.2005-11-092005-11-092005-11-09200510.1002/chem.200400825https://infoscience.epfl.ch/handle/20.500.14299/219852WOS:0002263335000036290In the presence of sulfur dioxide and an acid promoter, (-)-(1E,3Z)-2-methyl-1-((1S)-1-phenyleth- oxy)penta-1,3-dien-3-yl isobutyrate reacts with (Z)-3-(trimethylsilyloxy)-pent-2-ene giving a silyl sulfinate intermediate that undergoes, in the presence of palladium catalyst, a desilylation and retro-ene elimination of SO2 with formation of (-)-(1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-5-oxo-3-((1S)-1-phenylethoxy )-heptyl isobutyrate as major product. This ethyl ketone undergoes cross-aldol reaction with (2S)2-methyl-3-[(tert-butyldimethylsilyl)- oxy]propanal giving an aldol that is reduced into a stereoheptad corresponding to the C(19)-C(27)-segment of Rifamycins with high diastereoselectivity and enantiomeric excess.aldol reactionasymmetric synthesisDiels-Alder reactiondienespolypropionatessulfur dioxideBond-forming reactionstereoselective-synthesissulfur-dioxidemethyl sulfonesstereopentad subunits4-component synthesisorganic-synthesisc19-c27 fragmentrna synthesisansa chainsulfur-dioxideExpeditious asymmetric synthesis of a stereoheptad corresponding to the C(19)-C(27)-ansa chain of rifamycins: Formal total synthesis of Rifamycin Stext::journal::journal article::research article