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 u ...

in the synthesis of pharmaceuticals such as ephedrine and pseudoephedrine.

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(''R'')-PAC or (''R'')-(−)-phenylacetylcarbinol is identical to -PAC, referring to the outdated system.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 odo ...

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 (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 pape ...

'', ''

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 ...

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

, and the enzyme

pyruvate decarboxylase Pyruvate decarboxylase is an enzyme () that catalyses the decarboxylation of pyruvic acid to acetaldehyde. It is also called 2-oxo-acid carboxylase, alpha-ketoacid carboxylase, and pyruvic decarboxylase. In anaerobic conditions, this enzyme is ...

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, 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