Improved Methodology for the Preparation of Chiral Amines

Chapter 1
Introduction
1.1. Chiral Drugs
Chiral molecules form a large proportion of therapeutic agents. Drug chirality is considered a
major theme in the design, discovery, development, launching and marketing of new drugs.
Awareness of the importance of chirality comes from the fact that stereoselectivity is an
essential dimension in pharmacology. The recent development of bioanalytical tools led to a
better understanding of the importance of stereoselective phramacodyanmics and
pharmacokinetics of chiral drugs. In 1984 it was estimated that the total proportion of drugs
having chiral centre in the European market (Swedish survey) was 53%. [1] The percentage
increased up to 57% within less than three years. [2]
It was also estimated that 55% of the chiral drugs are used as a racemic mixture and the rest
is marketed as a single enantiomer. By the end of the last century, the market for chiral drugs
established major place in the overall global drug market. The situation totally changed in
this century. Pharmaceutical companies stopped developing racemic drugs; they only focus
on the synthesis of single enantiomeric drug entities.
First we have to clarify the concept of chirality. Chirality or handedness comes originally
from the Greek word cheir which means hand. One of the simplest definition of the word
chiral is given by Mislow: An object is chiral if and only if it is not superposable on its mirror
image; otherwise it is chiral. [3] From the definition it is clear that the term chiral refers to the
spatial property of the objects including molecules. It defines that the molecule is nonsuperposable
on its mirror image and does not refer to the stereochemical composition of the
bulk material. [4]
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