The chiral pool is a "collection of abundant enantiopure building blocks provided by nature" used in synthesis. In other words, a chiral pool would be a large quantity of common organic enantiomers. Contributors to the chiral pool are

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

s, sugars, and

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ar ...

s. Their use improves the efficiency of total synthesis. Not only does the chiral pool contribute a premade carbon skeleton, their chirality is usually preserved in the remainder of the reaction sequence. This strategy is especially helpful if the desired molecule resembles cheap enantiopure natural products. Many times, suitable enantiopure starting materials cannot be identified. The alternative to the use of the chiral pool is asymmetric synthesis, whereby achiral precursors are employed or racemic intermediates are resolved.

Examples

The use of the chiral pool is illustrated by the synthesis of the anticancer drug

paclitaxel Paclitaxel (PTX), sold under the brand name Taxol among others, is a chemotherapy medication used to treat a number of types of cancer. This includes ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical can ...

(Taxol). The incorporation of the C10 precursor verbenone, a member of the chiral pool, makes the production of paclitaxel more efficient than most alternatives. Chiral pool synthesis is used to build a part of epothilone (an alternative to paclitaxel) from readily available enantiopure (–)-pantolactone.

Other uses of the chiral pool

In addition to serving as building blocks in total synthesis, the chiral pool is tapped to produce asymmetric catalysts, chiral protecting groups, and

resolving agent Chiral resolution, or enantiomeric resolution, is a process in stereochemistry for the separation of racemic compounds into their enantiomers. It is an important tool in the production of optically active compounds, including drugs. Another term wi ...

s. ;Chiral ligands from the chiral pool : Asymmetric catalysis relies on chiral ligands, which in turn are generally derived from the chiral pool. For example enantiopure 2,3-butanediol, derived from abundantly available

tartaric acid Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt Salt is a mineral composed primarily of sodium chloride (NaCl), a c ...

, is used to synthesize chiraphos, a component of catalysts used for asymmetric hydrogenation: ;Chiral reagents from the chiral pool : Diisopinocampheylborane is an organoborane that is useful for asymmetric synthesis of secondary alcohols. It is derived by hydroboration of α-pinene, a common diterpene member of the chiral pool. ;Resolving agents from the chiral pool Many if not most of the common resolving agents are natural products or derivatives thereof. Illustrative is l- malic acid, a dicarboxylic acid that is found in apples. It is used to resolve α-phenylethylamine, a versatile resolving agent in its own right.

References

{{Organic reactions Organic chemistry