Phenylacetylcarbinol (PAC) is an organic compound that has two

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

s, one with R- and one with S-configuration. (R)-PAC, which is commonly called -PAC, is known as a

precursor Precursor or Precursors may refer to: *Precursor (religion), a forerunner, predecessor ** The Precursor, John the Baptist Science and technology * Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of unr ...

in the synthesis of pharmaceuticals such as

ephedrine Ephedrine is a central nervous system (CNS) stimulant that is often used to prevent low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred treatment. It is of unclear benefit in ...

and

pseudoephedrine Pseudoephedrine (PSE) is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It may be used as a nasal/sinus decongestant, as a stimulant, or as a wakefulness-promoting agent in higher doses. It was first characteri ...

Nomenclature

(''R'')-PAC or (''R'')-(−)-phenylacetylcarbinol is identical to -PAC, referring to the outdated system. (''R'')-PAC is the levo-rotating isomer of phenylacetylcarbinol. The IUPAC name of phenylacetylcarbinol is 1-hydroxy-1-phenylpropan-2-one. Synonyms are 1-hydroxy-1-phenyl-2-propanone and 1-Hydroxy-1-phenylacetone.

Production

(''R'')-PAC is widely synthesized by fermentation of

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...

and

dextrose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

. In this process, colonies of

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

(in particular, strains such as ''

Candida utilis Torula (''Cyberlindnera jadinii'') is a species of yeast. Use Torula, in its inactive form (usually labeled as torula yeast), is widely used as a flavoring in processed foods and pet foods. It is often grown on wood liquor, a byproduct of paper ...

'', ''

Torulaspora delbrueckii ''Torulaspora delbrueckii'' is a ubiquitous yeast species with both wild and anthropic habitats. The type strain of ''T. delbrueckii'' is CBS 1146T, equivalent to CLIB 230 or ATCC 10662etc. The type strain of ''T. delbrueckii'' CBS 1146 T was seq ...

'', or ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...

'') are cultivated and added to a broth of water,

, and the enzyme pyruvate decarboxylase in a vat. The yeast is left to grow for a period of time, after which the

is introduced into the broth. The yeast then ferments the benzaldehyde into (''R'')-PAC. Boiling point at 12mmHg is 124-125C. The majority of L-PAC is generated in pharmaceutical plants in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, as an intermediate precursor in the production of pseudoephedrine. There are also biochemical reactions where enzymes such as acetohydroxyacid synthase I from ''E. coli'' condense pyruvate and benzaldehyde into R-PAC. Such methods have much higher conversion rates in comparison to the conventional yeast fermentation.{{cite journal , doi = 10.1002/bit.20392 , pmid = 15685598 , title = Column flow reactor using acetohydroxyacid synthase I from ''Escherichia'' coli as catalyst in continuous synthesis of R-phenylacetyl carbinol , journal = Biotechnology and Bioengineering , volume = 89 , issue = 6 , pages = 733–740 , year = 2005 , last1 = Engel , first1 = Stanislav , last2 = Vyazmensky , first2 = Maria , last3 = Berkovich , first3 = Dvora , last4 = Barak , first4 = Ze'ev , last5 = Merchuk , first5 = Jose , last6 = Chipman , first6 = David M.

References

Acyloins Phenyl compounds