A Green and Sustainable Approach: Celebrating the 30th Anniversary of the Asymmetric l‐Menthol Process

Takasago has been devoted to producing l‐menthol since 1954, and our long history of manufacturing this important aroma chemical is reviewed here. The current asymmetric catalytic process had its 30th anniversary in 2013. Our l‐menthol process is considered carbon‐neutral, and, therefore, ‘green’ and sustainable. It uses renewable myrcene obtained from gum rosin as a starting material. In addition, the Rh‐BINAP (=2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl) catalytic system is highly efficient. This pathway not only leads l‐menthol, but a variety of 100% biobased aroma chemical products as well. By measuring the ¹⁴C levels in a material, one can determine the percentage of carbon that is biobased. This biobased assay, described as the ratio plant‐derived C/fossil‐derived C, can clarify how renewable a product really is. This will be highlighted for several of Takasago's key aroma chemicals.