Highly Functionalized Organolithium Reagents for Enantiomerically Pure α-Amino Acid Synthesis
摘要:
Highly functionalized L-serine-derived organolithium reagents have been generated and reacted with a variety of electrophiles, delivering novel enantiomerically pure adducts. These adducts were then converted into homochiral amino alcohols and novel nonproteinogenic alpha-amino acids, including an aspartic acid mimic that has been synthesized in an enantiomerically pure form for the first time.
Carbonylative coupling of organozinc reagents in the presence and absence of aryl iodides: synthesis of unsymmetrical and symmetrical ketones
作者:Richard F. W. Jackson、Debra Turner、Michael H. Block
DOI:10.1039/a606394b
日期:——
The utility of the palladium(0) catalysed reaction of the
iodoalanine-derived organozinc reagent 6a with functionalised
aryl iodides, under a carbon monoxide atmosphere, to give
protected 4-aryl-4-oxo α-amino acids 8, is illustrated by
a short synthesis of L-kynurenine 4. Treatment of
functionalised organozinc reagents with catalytic
tetrakis(triphenylphosphine)palladium(0) under an atmosphere of
carbon monoxide in the absence of any electrophile leads to the
formation of symmetrical functionalised ketones 9 in good yields.
This reaction is illustrated by a one-step synthesis of protected
(2S,6S)-4-oxo-2,6-diaminopimelic acid 9a from
commercially available compounds. It has been established that
adventitious molecular oxygen plays a key role in the formation
of the symmetrical ketones 9, and that rigorous exclusion of
oxygen can result in substantially higher yields of ketones 8 in
the cross-coupling with some aromatic iodides.
[reaction: see text] Catalytic, enantioselective Mannich-type reactions of alpha-imino estersbearing readily removable substituents on nitrogen are described. Several N-carbamate-protected alpha-imino esters, which are readily prepared from 2-bromoglycine esters using a polymer-supported amine, reacted with silicon enolates to afford the desired adducts in high yields with high enantioselectivity
available Boc-protected Z-alkenyl aminals could be used as Z-alkenyl and E-alkenyl imine precursors under acidic conditions. In the Mukaiyama–Mannich reaction of Z-alkenyl Boc-aminals, the E/Z geometry of the products was controlled by the catalyst used. The present method was also applied to asymmetric Mukaiyama–Mannich reactions.
Carbonylative coupling of an amino acid-derived organozinc reagent with functionalized aryl iodides: synthesis of kynurenine
作者:Richard F. W. Jackson、Debra Turner、Michael H. Block
DOI:10.1039/c39950002207
日期:——
The utility of the palladium(0) catalysed reaction of the serine-derived organozinc reagent 6 with functionalized aryl iodides, under a carbon monoxide atmosphere, to give protected 4-aryl-4-oxo α-amino acids 8 is illustrated by a short synthesis of L-kynurenine.
Stille reaction is designed for the first time, allowing for the construction of a rich range of C(sp3)−C(sp3), C(sp3)−C(sp2), and C(sp3)−C(sp) bonds in good to high yields with excellent stereoselectivity under exceptionally mild conditions. The innovative use of synergistic photoredox/nickel catalysis enables a novel single-electron transmetalation process of stannane reagents, providing a new research