Simple Plug‐In Synthetic Step for the Synthesis of (−)‐Camphor from Renewable Starting Materials

Abstract

Racemic camphor and isoborneol are readily available as industrial side products, whereas (1R)-camphor is available from natural sources. Optically pure (1S)-camphor, however, is much more difficult to obtain. The synthesis of racemic camphor from α-pinene proceeds via an intermediary racemic isobornyl ester, which is then hydrolyzed and oxidized to give camphor. We reasoned that enantioselective hydrolysis of isobornyl esters would give facile access to optically pure isoborneol and camphor isomers, respectively. While screening of a set of commercial lipases and esterases in the kinetic resolution of racemic monoterpenols did not lead to the identification of any enantioselective enzymes, the cephalosporin Esterase B from Burkholderia gladioli (EstB) and Esterase C (EstC) from Rhodococcus rhodochrous showed outstanding enantioselectivity (E > 100) towards the butyryl esters of isoborneol, borneol and fenchol. The enantioselectivity was higher with increasing chain length of the acyl moiety of the substrate. The kinetic resolution of isobornyl butyrate can be easily integrated into the production of camphor from α-pinene and thus allows the facile synthesis of optically pure monoterpenols from a renewable side-product.

Is Camphor the Future in Supporting Therapy for Skin Infections?

“…The α-pinene chemical was used as a substrate, from which an isobornyl ester was obtained. This ester was then subjected to kinetic separation using an esterase derived from Burkholderia gladioli to obtain pure (+)-isoborneol, from which, after oxidation, (-)-camphor was obtained [ 37 ].…”

Effect of rosemary addition on the sensorial and physicochemical qualities of dry-cured ham slices. Measurement of camphor transfer

“…At 14 days, camphor could be absorbed because fat is a lipophilic medium that absorbs apolar substances, such as aromatic compounds, reducing its content in the surface layer of the slices. The internal layers could become saturated at day 28 due to the rapid absorption from day 7 and the transformation of borneol to camphor [32,33]. At 60 days, the recovering of the initial values could be due to all layers absorbed the aromatic compounds and the method only detected camphor content in the surface layer.…”

“…Camphor, which has a characteristic camphoraceous odour and is used commercially as a moth repellent [27], is credited with specific bioactive effects such as anesthetic effect [28], pesticidal and insecticidal properties [29], antimicrobial activity [30] or mild expectorant activity [31]. In addition, it has a precursor borneol, another aromatic compound of rosemary, which is transformed into camphor and may cause the camphor content of rosemary to increase over time [32,33].…”

Recent Advances of Thiamine in Organic Synthesis

“…Green chemistry, also known as sustainable chemistry, aims to develop alternative and sustainable technologies to reduce or eliminate the use or generation of hazardous substances. [1] With this aim, a significant research effort has been dedicated towards the development of green solvents, [2] renewable starting materials, [3] electrochemistry, [4] photochemistry, [5] as well as biocatalysis, [6] and remarkable progress has been made. [7] Thiamine hydrochloride (VB 1 ), is the first recognized naturally occurring nutrient, which exhibit many superior properties in green chemistry [8] and biology.…”