ASYMMETRIC SYNTHESIS bpharm notes sem four

Assymetric syntheis

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

2. 2 TYPES 1. PARTIAL ASYMMETRIC SYNTHESIS 2. ABSOLUTE ASYMMETRIC SYNTHESIS

3. 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

4. Resulting product – levorotatory Unequal amounts due to the different rate of decomposition of diastereomers I and II

5. Reduction of pyruvic acid to lactic acid in presence of optically active alcohols –ml-menthol, l- pentyl alcohol or l- borneol

6. 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

7. 1 st absolute assymetric synthesis by W.Kuhn et. Al(1929) irradiated the racemic modification of ethyl alpha bromopropionate with RCPL/LCPL of wabelength 2800 o A—compound with rotation +0.05 o and -0.05 o Kuhn and Knopf (1930) irradiated (dl) α - azidopropionic dimethylamide with RCPL----Compound with+0.78 With RCPL ----Product of -1.04

8. SIGNIFICANCE OF ASYMMETRIC SYNTHESIS   synthesis of pharmaceuticals, natural products, and agrochemicals (mainly fungicides, herbicides, insecticides, and pheromones)

9. SYNTHESIS OF METOPROLOL