Advances in Flavours and Fragrances from the Sensation to the Synthesis

Advances in Flavours and Fragrances From the Sensation to the Synthesis Advances in Flavours and Fragrances From the Sensation to the Synthesis Edited by Karl A.D. Swift Quest International, Ashford, Kent, UK RSeC ROYAL SOCIETY OF CHEMISTRY The proceedings of Flavours and Fragrances 2001 : From the Sensation to the Synthesis held on 16-18 May 2001 at the University of Wanvick, Coventry, UK. Special Publication No. 277 ISBN 0-85404-82 1-9 A catalogue record for this book is available from the British Library 0 The Royal Society of Chemistry 2002 All rights reserved. Apart from any fair dealing for the purpose of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 OW, UK Registered Charity No. 207890 For further information see our web site at www.rsc.org Printed in Great Britain by TJ International Ltd, Padstow, Cornwall Preface This book is a compilation of sixteen of the twenty papers presented at the 2001 RSC/SCI flavours and fragrances conference at Scarman House, University of War- wick. The meeting was spaced over two and a half days and saw speakers and delegates from all corners of the world exchanging ideas and information. The aim of the meeting was to bring together scientists from both industry and the academic world, who have a cornmon interest in the chemistry of flavours and fragrances. The subject matter was intentionally broad, covering areas such as biochem- istry of receptors/structure activity relationships, analytical techniques, natural products/essential oils, organic and bioorganic chemistry, and flavours/foods. The book is divided into the same sections as the original meeting. The chapters contained in this book have been rapidly edited and proof read by the editor only. Every effort has been made to ensure that no mistakes are present but inevitably it is likely that some still exist! The editor also asks that the reader is understanding of the fact that most chapters have been written by people who are not native English speakers. Finally, I would like to thank everybody who contributed to the 2001 conference and made it such a success. Contents Structure Activity Relationships Structure Activity Relationships and the Subjectivity of Odour Sensation 3 Thomas Markert Relationship of Odour and Chemical Structure in 1- and 2-Alkyl Alcohols and Thiols 15 Y. Sakoda and S. Hayashi Analytical New Developments in Sorptive Extraction for the Analysis of Flavours and Fragrances 27 P. Sandra, F. David and J. Vercammen Application of Chromatographic and Spectroscopic Methods for Solving Quality Problems in Several Flavour Aroma Chemicals 39 Michael Zviely, Reuven Giger, Elias Abushkara, Alexander Kern, Horst Sommer, Heinz-Juergen Bertram, Gerhard E. Krammer, Claus Oliver Schmidt, Wolfgang Stumpe and Peter Werkhoff Natural Products and Essential Oils Commercial Essential Oils: Truths and Consequences 57 Brian Lawrence Stable Isotopes for Determining the Origin of Flavour and Fragrance Components: Recent Findings 84 Daniel Joulain Fragrant Adventures in Madagascar: The Analysis of Fragrant Resin from Canarium madagascariense 92 Robin Clevy The Effect of Microgravity on the Fragrance of a Miniature Rose, ‘Overnight Scentsation’ on Space Shuttle (STS-95) 99 Braja D. Mookherjee, Subha Pate1 and Weijia Zhou vii ... Vlll Advances in Flavours and Fragrances Organic and Bioorganic Chemistry Ambergris Fragrance Compounds from Labdanolic Acid and Larixol 113 Aede de Groot The Synthesis of Fragrant Cyclopentanone Systems 127 Helen C. Hades Designing Damascone- and Ionone-like Odorants 138 Philip Kraft Creation of Flavours and the Synthesis of Raw Materials Inspired by Nature 147 Mark L. Dewis and L. Kendrick Flavours/Foods New Results on the Formation of Important Maillard Aroma Compounds 163 Peter Schieberle and Thomas Hofmann Out of Africa: The Chemistry and Flavour Properties of the Protein Thaumatin 178 Steve Pearce and Hayley Roth Stability of Thiols in an Aqueous Process Flavour 194 Chris Winkel, Paul B. van Seeventer, Hugo Weenen and Josef Kerler High Impact Aroma Chemicals 202 David J. Rowe Subject Index 227 Structure Activity Relationships STRUCTURE ACTIVITY RELATIONSHIPS AND THE SUBJECTIVITY OF ODOUR SENSATION Dr. Thomas Markert Cognis Deutschland GmbH, Henkelstr 67, D 4055 1 Duesseldorf, Germany 1 INTRODUCTION Structure activity relationships (SAR) are one of the most useful sets of tools in both pharmaceutical and fragrance research. Ever since Amoore carried out his studies and formulated his theory of odour recognition, chemists have been looking at the shape of molecules and their associative possibilities to find clues that would explain perceived odour sensations. How difficult it is to go down this research path in finding new chemical entities with interesting odour qualities is clear from the broad variety of odours the human nose is able to detect and identify. I will now attempt to explain how complex the activity side of SAR can be and what the consequences of this complexity are. In this context I will again follow up the question which Pieter Aarts recently put at the top of an article [l], although he was dealing with a totally different subject: “The Optimal Fragrance - Lucky Shot or Organised Hunt?” The sense of smell is even able to discriminate between the antipodes of chemical structures like R- and S-carvone or R- and S-p-menthene-8-thiol [2]. When a perfume layman, like a chemist, tries to verify the reported odour descriptions, he becomes aware that the difference between the odours of chemically similar substances is dependent on purity, concentration in your nose, your sniffing technique, the way the air streams through your nose [3], and much more. As Charles Sell tells us in a remarkable report about structure/odour correlations entitled “The Mechanism of Olfaction and the Design of Novel Fragrance Ingredients” [4], it is sometimes a trace impurity which fundamentally changes the scent of a substance or a mixture of substances. 2 AMOORE’S CONCEPT OF PRIMARY ODOURS Let us start with John E. Amoore’s [5] theory of odour reception (figure l), which is based on specific anosmia and the concept of primary odours. What I understand about his idea is that he tried to find chemical structures by using the holes in the olfactory epithelium and a negative selection of substances that were reported as resulting in specific anosmia. 4 Advances in Flavours and Fragrances HIGH L< ODOR THRESHOLD CONCENTRATION (log2) Figure 1 John E. Amoore 's theory of odour reception In terms of SAR, this would mean he was searching for chemicals with no activity. And from the shape of the molecules he found in this way he tried to reconstruct a receptor site which could in size and shape accept this chemical structure (figure 2). The goal of his studies was a classification of odours by collecting groups of similar molecules, which could fit, specifically into the same receptor. Amoore was limited in his approach to the choice of known substances and he was also dependent on the odour descriptions he was given by the experts. My opinion in this context is that Amoore could never definitely know whether a substance, which would bind to the same specific receptor, would cause the same odour sensations and associations. In other words, he grouped various chemicals together, guided by the similar odour descriptions for those materials. Figure 2 3 SPECIFIC ANOSMIA AND THE CONCEPT OF PRIMARY ODOURS I have to admit at this point that I have a problem. My problem is with specific anosmia, which is the basis of Amoore's theory of olfaction. The way Amoore measured specific anosmia demonstrated the usefulness of his approach and proved the reality of this phenomenon. However, the results are not useful to classify scents; they only caused chemists to focus on molecules for which there would probably be a specific receptor in the nasal mucous membrane. When a chemist looks at the structures found by Amoore they are surprised to find four small molecules like trimethylamine and isobutyric aldehyde, alongside two very large molecules like androstenone and pentadecanolide (figure 3). Structure Activity Relationships 5 Figure 3 Structure activity relationships and the subjectivity of odour sensation Those who are able to smell androstenone with 19 carbon atoms describe it as reminding them of stale sweat. Isovaleric acid, a molecule with 5 carbon atoms, is almost officially said to smell sweaty. So, am I to believe that a molecule with 19 carbon atoms is bound to the same specific receptor as a similarly smelling compound containing 5 carbon atoms? The Axnoore approach is most interesting because, when you think about it, in the end it doesn’t tell you much about the structural side of SAR, nor does it tell you much about the activity on the side of the receptor, but it raises the question of what specific anosmia means. What is the sense of lacking receptors? When we at Cognis were searching for new sandalwood substances, I noticed that I became anosmic to Sandelice@;first only on Fridays, then later all the time (figure 4).

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