Co-reporter:Roberto M. Risi, Andrew M. Maza, and Steven D. Burke
The Journal of Organic Chemistry 2015 Volume 80(Issue 1) pp:204-216
Publication Date(Web):November 14, 2014
DOI:10.1021/jo502301k
Four different Rh-catalyzed asymmetric hydroformylation (AHF) tandem reactions have been developed in the context of the total syntheses of (+)-patulolide C, (−)-pyrenophorol, (+)-decarestrictine L, and (+)-Prelog–Djerassi lactone. A total synthesis of (+)-patulolide C has been accomplished in three steps utilizing a Rh(I)-catalyzed Z-selective anti-Markovnikov hydroacetoxylation of a known alkyne to give a Z-enol acetate with excellent selectivity. An AHF/intramolecular Wittig olefination cascade was utilized to set the C4-hydroxyl stereochemistry, E-olefin geometry, and form the macrolactone. In addition, both (−)-pyrenophorol and (+)-decarestrictine L have been synthesized from the enantiomeric (4R)- and (4S)-4-(tert-butyldimethylsiloxy)-1-pentyne in five and four steps, respectively. These syntheses feature Ru(II)-catalyzed Z-selective anti-Markovnikov hydroacetoxylation of terminal alkynes followed by AHF/Wittig olefination sequences to rapidly establish functionality and stereogenicity. A synthesis of (+)-Prelog–Djerassi lactone was accomplished in three isolations from the known 1-vinyl-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane ortho ester. An AHF/crotylation tandem sequence has been developed to set the C2–C4 stereochemistry. An asymmetric hydrogenation was employed to set the C6 stereochemistry, resulting in an especially efficient enantioselective synthesis from achiral starting material. In summary, these syntheses have greatly improved efficiency in terms of atom-economy, catalytic stereoselective transformations, inexpensive reagents, step-counts, and overall yield when compared with previous synthetic attempts.
Co-reporter:Roberto M. Risi and Steven D. Burke
Organic Letters 2012 Volume 14(Issue 10) pp:2572-2575
Publication Date(Web):May 4, 2012
DOI:10.1021/ol3008765
A synthesis of the Prelog–Djerassi lactone [(+)-1] has been accomplished in three isolations and 57% overall yield from the known vinyl ortho ester 2. A Rh(I)-catalyzed asymmetric hydroformylation/crotylation tandem sequence has been developed and used to set the C2–C4 stereochemistry. A Rh(I)-catalyzed asymmetric hydrogenation was employed to set the C6 sterechemistry, resulting in an unusually short and efficient enantioselective synthesis of this touchstone molecule from achiral starting material.
Co-reporter:Roberto M. Risi and Steven D. Burke
Organic Letters 2012 Volume 14(Issue 4) pp:1180-1182
Publication Date(Web):February 3, 2012
DOI:10.1021/ol2034299
A highly atom-economical total synthesis of (+)-patulolide C has been accomplished in three steps from the known (2R)-8-nonyn-2-ol in 49% overall yield and 93% de. A Rh(I)-catalyzed asymmetric hydroformylation (AHF)/ intramolecular Wittig olefination cascade was utilized to set the C4-hydroxyl stereochemistry and E-olefin geometry as well as form the macrolactone.
Co-reporter:Alexander J. L. Clemens and Steven D. Burke
The Journal of Organic Chemistry 2012 Volume 77(Issue 6) pp:2983-2985
Publication Date(Web):February 27, 2012
DOI:10.1021/jo300025t
Both enantiomers of Garner’s aldehyde (3) are prepared from the same alkene 4 by catalytic asymmetric hydroformylation.
Co-reporter:Brian S. Lucas Dr.;Vijayagopal Gopalsamuthiram Dr.;Steven D. Burke
Angewandte Chemie International Edition 2007 Volume 46(Issue 5) pp:
Publication Date(Web):13 DEC 2006
DOI:10.1002/anie.200603656
Challenge met: In the synthesis of phorboxazole B, a highly efficient hetero-Diels–Alder reaction was used to construct the key C33–C39 linchpin, allowing for the completion of the C18–C46 fragment (see picture). Coupling with a suitable C3–C17 partner was followed by late-stage formation of the oxazole unit, macrocyclization, and deprotection to afford synthetic phorboxazole B.
Co-reporter:Brian S. Lucas Dr.;Vijayagopal Gopalsamuthiram Dr.;Steven D. Burke
Angewandte Chemie 2007 Volume 119(Issue 5) pp:
Publication Date(Web):13 DEC 2006
DOI:10.1002/ange.200603656
Ziel erreicht: Bei der Synthese von Phorboxazol B wurde mit einer hocheffizienten Hetero-Diels-Alder-Reaktion das zentrale C33-C39-Schlüsselelement erhalten, mit dem das C18-C46-Fragment vervollständigt werden konnte (siehe Bild). Der Kupplung mit einem geeigneten C3-C17-Partner folgten die späte Bildung der Oxazoleinheit, die Makrocyclisierung und das Entschützen zu synthetischem Phorboxazol B.