The formation of amides and peptides often necessitates powerful yet mild reagent systems. The reagents used, however, are often expensive and highly elaborate. New atom-economical and practical methods that achieve such goals are highly desirable. Ideally, the methods should start with substrates that are readily available in both chiral and non-chiral forms and utilize cheap reagents that are compatible with a wide variety of functional groups, steric encumberance, and epimerizable stereocenters. A direct oxidative method was developed to form amide and peptide bonds between amines and primary nitroalkanes simply by using I2 and K2 CO3 under O2 . Contrary to expectations, a 1:1 halogen-bonded complex forms between the iodonium source and the amine, which reacts with nitronates to form α-iodo nitroalkanes as precursors to the amides.
The C19 diterpenoid
alkaloids (C19 DTAs) are a large family of
natural products, many of which modulate the activity of ion channels
in vivo
and are therefore of interest for the study of neurological
and cardiovascular diseases. The complex architectures of these molecules
continue to challenge the state-of-the art in chemical synthesis,
particularly with respect to efficient assembly of their polcyclic
ring systems. Here, we report the total syntheses of (−)-talatisamine,
(−)-liljestrandisine, and (−)-liljestrandinine, three
aconitine-type C19 DTAs, using a fragment coupling strategy. Key to
this approach is a 1,2-addition/semipinacol rearrangement sequence
which efficiently joins two complex fragments and sets an all-carbon
quaternary center.
The formation of amides and peptides often necessitates powerfuly et mild reagent systems.T he reagents used, however,a re often expensive and highly elaborate.N ew atom-economical and practical methods that achieve such goals are highly desirable.I deally,t he methods should start with substrates that are readily available in both chiral and non-chiral forms and utilize cheap reagents that are compatible with awide variety of functional groups,steric encumberance, and epimerizable stereocenters.Adirect oxidative method was developed to form amide and peptide bonds between amines and primary nitroalkanes simply by using I 2 and K 2 CO 3 under O 2 .C ontrary to expectations,a1:1h alogen-bonded complex forms between the iodonium source and the amine,w hich reacts with nitronates to form a-iodo nitroalkanes as precursors to the amides.
The formation of quaternary stereogenic centers via convergent fragment coupling is a longstanding challenge in organic synthesis. Here, we report a strategy for the formation of quaternary stereogenic centers in...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.