Olfactory Chemistry: Polycyclic Musks-What Clean Smells Like

One of the best things about science is it is always evolving and chemistry is no different. As a synthetic chemist I am always looking for the next new reaction that will allow me to easily make the next new molecules I am interested in. What is true for me as a medicinal chemist was also true for the chemists who worked in the fragrance industry. In the post-World War 2 economy there were a lot of chemical by-products being formed and clever chemists were using them to develop new plastics and pharmaceuticals and, yes, aromachemicals. Along with new chemical techniques allowing a chemist to make another ring of atoms fused to the same ring used in the nitro musks the polycyclic musks were born.

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In 1951, the first polycyclic musk was synthesized by Kurt Fuchs and it was called Phantolide. It didn’t have a very strong odor but it had incredible stability and ability to stay concentrated even in water it became a natural to be added to detergents as this would stick to the clothes after washing. This was the main use of polycyclic musks for many years until 1965 and the synthesis of Galaxolide by M.G.J. Beets at International Flavors and Fragrances. As you can see above Dr. Beets used the new synthetic methods to take the two groups on the right and cyclize them. His hypothesis was if he kept the oxygen in a similar spacing as it was in in Phantolide he might make an improvement, and he did. Galaxolide retained the stability and properties that made it a good detergent additive but it now also had a more concentrated odor profile and could also be used in perfumery. Perfumer Sophia Grojsman would end up using it in a 21% concentration in her masterpiece Lancome Tresor in 1990.

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This would open the door for other chemists to find other polycyclic musks and when you make the simple change of making the five-membered ring on the left of Phantolide a six-membered ring you get Fixolide. When you completely change the ring on the right-hand side of Phantolide you get Cashmeran. If you want to smell what these three molecules smell like together The Body Shop’s White Musk contains all of these. If you do that you will understand why these are referred to as the “clean” musks as they evolved from their beginnings as laundry detergent odorants to key components of the “clean and fresh” movement in perfume.

Mark Behnke

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