The substances used as the starting point for these syntheses are in general not chiral. The trick is to make the product chiral. This is done using a chiral catalyst molecule. Suppose we compare this molecule with a left hand. A left hand will make a better match in a handshake with another left hand (one of the two emerging product forms) than with a right hand (the other form of the product). Thus a chiral catalyst can control production of the desired chiral product.