1. ASYMMETRIC SYNTHESIS
THE DIRECT(WITHOUT RESOLUTION) SYNTHESIS OF AN OPTICALLY
ACTIVE COMPOUND FROM A SYMMETRIC COMPOUND(OPTICALLY
INACTIVE) WITH OR WITHOUT THE USE OF OPTICALLY ACTIVE REAGENT
6. PARTIAL ASYMMETRIC SYNTHESIS
• Synthesis of optically active compound directly (without resolution)
from a symmetrical compound by the intermediate use of an optically
active compound
• Marckwald in 1904- valeric acid from methyl ethyl malonic acid using
- brucine
7.
8. • Resulting product – levorotatory
• Unequal amounts due to the different rate of decomposition of diastereomers I and II
9. Reduction of pyruvic acid to lactic acid in presence of optically active alcohols –ml-
menthol, l-pentyl alcohol or l-borneol
10.
11.
12. ABSOULTE ASYMMETRIC
SYNTHESIS/ABSOLUTE DECOMPOSITION
• Formation of an optically active compound from inactive one, without
the intermediate use of optically active reagent but using right /left
circularly polarized light
• Circularly polarized light may be obtained by passing plane polarized
light through a specially cut glass prism known as Fresnel’s rhomb
13. • 1st absolute assymetric synthesis by W.Kuhn et.
Al(1929)
irradiated the racemic modification of ethyl alpha
bromopropionate with RCPL/LCPL of wabelength
2800o A—compound with rotation +0.05o and -0.05o
• Kuhn and Knopf (1930) irradiated (dl) α-
azidopropionic dimethylamide with RCPL----
Compound with+0.780
• With RCPL ----Product of -1.040
14.
15. SIGNIFICANCE OF ASYMMETRIC SYNTHESIS
• synthesis of pharmaceuticals, natural products, and agrochemicals
(mainly fungicides, herbicides, insecticides, and pheromones)