Levorotatory substance

If the rotation is in a clockwise direction, the substance in solution is said to be dextrorotatory [d or (+)]. Rotation in the counter clockwise direction infers a levorotatory substance... 

Levorotatory (Section 9.3) An optically active substance that rotates the plane of polarization of plane-polarized light in a left-handed (counterclockwise) direction. 

A substance that rotates plane-polarized light in the clockwise direction is said to be dextrorotatory, and one that rotates plane-polarized light in a counterclockwise direction is said to be levorotatory (Latin dexter, right and laevus, left). 

The first experiments made by Neuberg and Nord with the simplest diketone, diacetyl, showed at once that this substance can be hydrogenated phytochemically with comparitive ease. Acetylmethylcarbinol appears as an intermediate (see below), and the end product of reduction is asymmetric and levorotatory. Reduction was effected by the action of fermenting yeast on diacetyl. The 2,3-butanediol that is formed can be isolated by alcohol-ether extraction of the fermentation mixture after concentration in the Faust-Heim apparatus or by steam distillation in an atmosphere of carbon dioxide under ordinary pressure it is then carefully concentrated with the birectifier and obtained in the pure state by final fractionation. 

Halving the concentration or the tube length would halve the number of optically active molecules and the new rotation would be +30° if the substance was dextrorotatory or -150° if levorotatory. 

A clockwise rotation, as the observer looks towards the beam, defines the substance as dextrorotatory (i.e., rotates to the right) and the angle a is taken as a positive (+) rotation. If the rotation is counterclockwise the substance is described as levorotatory (i.e., rotates to the left) and the angle a is taken as a negative (—) rotation. 

When acidic hydrolysis is carried out with the material supposed to be enammonium salt, (+)a-phenylpropionaldehyde is produced in excess. When the same substance is heated at 60°C for several hours, a levorotatory material is produced in excess. 

It has been suggested that there may be some benefit of using tryptophan in selected patients, particularly those with psychomotor retardation (3). Unfortunately, most of these reports have appeared as letters to the editors of journals (4-6) or as preliminary communications (7). In addition to the possible absence of any consistent effect, there are many plausible reasons to explain the variability in response. Tryptophan has been given in both the racemic and monomeric (levorotatory) forms, both alone and together with a number of substances intended to increase the synthesis or availability of serotonin, including monoamine oxidase (MAO) inhibitors (8), potassium or carbohydrate supplements (9), and co-enzymes such as pyridoxine or ascorbic acid (10). It has also been... 

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