Organic synthesis

Stratergies for synthesis of chiral compounds.
1. Use chiral starting material (chiral pool synthesis: amino acids, carbonhydrates, alkloids, etc)
B  + C ---> P*

pros: 100% of enatiomers was synthesized
          Economical by saving steps.
Cons: The chiral reagents may not be available
           only one enantiomers existed
2. Resolution of racemate
S ---------P*(50% of P*R and 50% of P*S)
Pros: can used available separation technique to purify such as chromatography, distillation, crystalization
Racemic mixtrues are easy to obtain, both enatiomers can be accessed
Cons: not economical if needed only one enantiomer.
3. Assymetric synthesis
a, Substrate control
- a chiral reagents are used
  S* --------(R)----> P*
Pros: Easy, economical
Cons: Hard to control reactions how much percents of Products.
- Chiral auxiliaries
S + A*-------> S-A*------(R)------->P*-A ---(-A)---> P*
Pros: flexible if both +A and -A* available
can separate diastereomers before cleaving auxiliaries
Cons: too extra steps
           Auxiliaries might be expensive
b, chiral reagents
S + R*----> P*
Pros: save steps, flexible if both +R* or -R* are available
cons: few available reagents
Mixture of enantiomers need to purify them.
c, chiral catalyst
Terms:  
Enatiomers is one of two stereoisomers that are mirror images of each other that are non-superposable (not identical), much as one's left and right hands are the same except for opposite orientation
Diastereomers (sometimes called diastereoisomers) stereoisomers that are not enantiomers.^. Diastereomerism occurs when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.