Page 13 - Demo-1

Chemical Dynamic Kinetic Resolution: Displacements via Chiral Auxiliaries ! Chiral sultam facilitates highly selective SN2 DKR
Me
Me Me
O CHCN O2 BnNH O
Me
O
Me
Me
Me
S O2
N
S Br
N Me Br
32
N Me NBn2
reflux
quantitative
100% de
Me Me
S Br O2
S O2
enantiopure
O
Me
N
Ward, Tet. Asymm., 1995, 6, 1475.
see also: Nunami, JOC, 1995, 60, 6776. Durst, JOC, 1998, 63, 3117.
Caddick, Tet., 2001, 57, 6589.
OMe N
SM epimerizes under reaction conditions; one diastereomer much more reactive than the other
epimerizing
! Hydrazones amenable to moderately selective alkylation
N
Me
i. BF3OEt2 OMe
OMe OMe NN
90% yield 69% de
TMSO ii. MeO
iii. Na2CO3
Me
N
OAc Me Me
BF3OEt2 N
N
NMe Me
Me OMe
Me Me O
Enders, Tet. Asymm., 1998, 9, 2155.
OAc Me
epimerization
OAc Me Me
Biocatalytic Dynamic Kinetic Resolution: Enzymatic Reduction ! Relatively simple substrates are reduced in biocatalytic DKR
81% yield > 98% ee > 98% de
EtO
EtO
EtO
OO
Me
OO
Me
OO
Me
Me
Me
Recombinant E. coli
expressing Gre3p
kfast
Recombinant E. coli
expressing Gre3p
kslow
Recombinant E. coli
expressing Gre3p
EtO
O OH
Me
Me
O OH
EtOMe
Me
O OH
Recombinant E. coli express enzymes from Baker's yeast which catalyze DKR.
87% yield > 98% ee > 98% de
EtO
Me
Stewart, JOC, 2000, 65, 2586.