Chemoselective Protection of α-Ketoacids by Direct Annulations with Oximes
作者:Melissa A. Flores、Jeffrey W. Bode
DOI:10.1021/ol100467t
日期:2010.5.7
Oximes and alpha-ketoacids undergo an unexpectedly facile and chemoselective annulation to afford 2,5-dihydrooxazole 3-oxides. The resulting cyclic nitrones serve as chemically and configurationally stable masked a-ketoacids that can be easily elaborated and manipulated. Deprotection is achieved by mild reduction with zinc metal and hydrolysis. This methodology allows for the protection, elaboration, and deprotection of enantiopure peptide derived, a-ketoacids, which are the key starting materials for the chemoselective ketoacid-hydroxylamine peptide ligation.
Total Synthesis of the Natural Herbicide MBH‐001 and Analogues
作者:Birgit Kuhn、David M. Barber、Hansjörg Dietrich、Uwe Döller、Michael G. Hoffmann、Dirk Schmutzler、Stefan Schnatterer、Martin E. Maier、Tamer Kocakaya、Marius Morkunas
DOI:10.1002/ejoc.202000294
日期:2020.4.23
Cyclic nitrones are the key: A flexible route to the natural herbicide MBH‐001 was developed. As opposed to azlactones, the use of the corresponding nitrones secured the regiochemistry (2 vs. 4‐position) in the aldol type reaction of the anions with aldehydes. The work also led to the determination of the relative and absolute stereochemistry of MBH‐001.