Page 20 - Demo-1
P. 20
Examples of Racemization (Cont'd)
5) Anionic interconversion
ON
Et (-)-sparteine
6) Racemization via π-allyl intermediates
R1 R2 [M] R1 R2
Nu M 7) Racemization via SN2 processes
s-BuLi NOLiL NOLiLE NOE
Nu R1 R2
Br
CO2Me
C. rugosa
PPh3 Br
Br
Nu
CO2H
79% ee, 78% yield
The "Catalytic Triad" - Reaction Mechanism of CALB
Asp187 Asp187
OO OOOR1O
O
R2
O Ser105
H N N
His224
H O Ser105
R1O R2
H N N H
His224
Asp187
R3 O
R4 O R2
Asp187
R3
R O
R1 O OO4OR OOOR
22
H N N
224
H
O Ser105
H N N H O Ser105 OH 224
His
Pamies, O; Backvall, J-E. Chem. Rev. 2003, 103, 3247
R1OH
RR His 34
