The Allure of Mass Spectrometry: from an Earlyday Chemist’S Perspective

THE ALLURE OF MASS SPECTROMETRY: FROM AN EARLYDAY CHEMIST’S PERSPECTIVE Laszl oT ok} es* 4133 Thain Way, Palo Alto, CA 94306 Received 6 January 2016; accepted 9 February 2016 Published online 21 March 2016 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mas.21499 This reminiscing review article is an account of the author’s Keywords: steroids; stable isotope labeling; fragmentation fascination and involvements with mass spectrometry from the mechanisms; stereospecific fragmentation; bile steroids; TCDD; perspective of an organic chemist with an interest in natural bisphenol-A; instrumental developments; Asilomar Conference product chemistry. It covers a period from 1961 through the on Mass Spectrometry; Bay Area Mass Spectrometry mid 1990s as mass spectrometry evolved form a novelty technique to become a most widely used analytical technique. Following a brief synopsis of my pathway to mass spectrometry, my research efforts in this field are presented with a focus I. INTRODUCTION mainly on evolving principles and technologies which I had personal involvements with. To provide historical perspectives, By professional training I am an organic chemist with a long discussions of these developments are accompanied by brief standing fascination with natural product chemistry, probing the outlines of the relevant state-of-the-art, shedding light on the chemical bounties and mysteries of Mother Nature. Synthetic technical and conceptual challenges encountered during those organic chemistry and natural product chemistry share a early days in mass spectrometry. Examples are presented of my fundamental need for structural elucidations. In the late 1950s involvements with basic and applied research in mass spec- and at the beginning of the 1960s there were only a limited trometry during graduate studies at Stanford University and number of readily available analytical tools for structure close to three decade tenure in pharmaceutical research at identifications. These included IR and UV spectroscopy, combus- Syntex Research. My basic research interests focused mainly on tion-based elemental analyses and for configurational studies principles of electron ionization induced fragmentation mecha- optical rotation, optical rotatory dispersion (ORD) and circular nisms, with an emphasis on steroids and other model com- dichroism (CD). NMR spectroscopy was in baby shoes with the pounds. Extensive deuterium labeling evidence was used to introduction of the first commercial 60 MHz instruments by determine the fragmentation mechanisms of the diagnostically Varian, Palo Alto, CA in 1961. The low sensitivity of these NMR significant ions in the spectra of numerous model compounds, instruments, requiring 20 mg or more samples for a meaningful uncovering examples of wide-ranging hydrogen transfers, analysis, prevented their application to samples available only skeletal rearrangements, methyl and phenyl migrations, stereo- from small scale preparations. NMR gained widespread use later selective fragmentations and low and high energy fragmenta- in the 1960s with the introduction of the 100 MHz and Fourier tion processes. Depiction of the industrial research phase of my Transform (FT) instruments which reduced the sample require- career includes comments on the pivotal role mass spectrometry ment by ten fold and provided far more structural information. played on advancing modern pharmaceutical research. Exam- In search for new analytical methods, attention turned to ples are presented of involvements with instrumental develop- mass spectrometry (MS) as a technique with potentials to ments and a few select cases of applied research, including provide a wealth of structural information on sub-milligram studies of bile mechanisms in vertebrates, identification of amount of samples. Mass spectrometry had been in use already bisphenol-A leaching from sterilized polycarbonate containers, during and after the Second World War in the petroleum industry high sensitivity TCDD analyses and other projects. Reflecting to analyze volatile hydrocarbons. In the 1950s a select group of on my services for the mass spectrometry society, involvements pioneering investigators experimented with its application to with the co-founding and 12 year chairing of the Asilomar non-petrochemical, lower volatility compounds demonstrating Conference on Mass Spectrometry and founding of the Bay its potential usefulness in general organic chemistry. Their Area Mass Spectrometry regional MS discussion group, as part reports were impressive and by the time I started my graduate of my services for the mass spectrometry community, are studies in 1961 mass spectrometry was already considered an presented in some detail. # 2016 The Authors. Mass exciting new technique with great potentials for becoming a Spectrometry Reviews Published by Wiley Periodicals, Inc. major analytical tool for structural elucidations. In this review I Mass Spec Rev 36:520–542, 2017 intend to show how I succumbed to this appeal and how mass spectrometry became my career long scientific interest. My involvement in this field spans the period from mass spectrometry being the domain of mostly spectroscopists, This is an open access article under the terms of the Creative Commons physicists and geochemists, through its evolution to become a Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly most widely used analytical technique with current applications cited, the use is non-commercial and no modifications or adaptations in virtually every scientific and medical field. This review are made. focuses on developments in organic chemistry applications ÃCorrespondence to: 4133 Thain Way, Palo Alto 94306, CA. which I had personal involvements with, including comments on E-mail: [email protected] their relevance to the contemporary state-of-the-art. A brief Mass Spectrometry Reviews, 2017, 36, 520–542 # 2016 by The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc. ALLURE OF MASS SPECTROMETRY & overview of some of my research contributions in this field is for me and led to my career decision to become a chemist. A presented, concentrating more on conceptual descriptions rather dramatic change in this phase of my life occurred on October 23, than technical details, followed by examples of applications of 1956. As I was preparing a laboratory scale batch of 17a- mass spectrometry in the pharmaceutical industry and the role ethynyl-estradiol the news broke that thousands of people were this technique played in the advancement of modern pharmaceu- gathering in front of the Parliament building, demanding tical research. freedom of the press and other issues which were delineated in a During the second half of the 20th century, exponential ten point declaration. I left work in a hurry and headed to the growth in the use and instrumental developments in mass Parliament where I witnessed what had become the start of the spectrometry created a rapidly growing scientific community 1956 Hungarian Revolution against the Soviet occupation. That dedicated to this field. My contributions to the professionalism was the last day I set foot in Chinoin as an employee. of this emerging society are outlined in Section V. Two After a brief period of gaining freedom, on November 4 the contributions with lasting consequence for the society, the co- revolution was brutally crushed by the invading Soviet Army. founding and 12 year chairing of the Asilomar Conference on Due to concerns for my safety in Budapest and the obvious Mass Spectrometry, an international research conference series, return of political repression in the country, on December 26 I and involvements with the founding of Bay Area Mass decided to join the exodus of some two hundred thousand Spectrometry, a regional MS discussion group, are discussed in refugees from Hungary with the then living members of my some detail in Sections V(A) and V(B). family—mother, younger brother and an older cousin. After an all night march in pitch dark, through deep-plowed fields II. PATHWAY TO MASS SPECTROMETRY covered with two feet of snow, and dodging the occasional search lights and wildly shooting inebriated Russian border Sharing an incident commonly mentioned in the autobiographies patrols by hiding in the snow, we were fortunate to make it to of many noted scientists who were born in the first half of the Austria on our first trial—bloodied by frost bites but free at last. 20th century, and so eloquently depicted by Oliver Sacks in his We stayed in Austria for 6 months in refugee camps but by this epic biographical book, “Uncle Tungsten; Memories of a Chemi- time the US quota for Hungarian immigrants was already full. cal Boyhood” (Sacks, 2001), I too got interested in chemistry by However, with the aid of an affidavit from a distant relative having received a chemistry kit at age 11. In 1948, in the war living in California, and most probably by the insistence of my ravaged city of Budapest, Hungary, this kit was prepared by an brother and I that we wanted to attend university in the USA, in entrepreneurial young man who had a complete disregard, or lack June 1957 we were allowed to immigrate to the US as a “family of comprehension, of safety considerations. It came with no consolidation” case. My brother, Zoltan A. Tok} es, in time instructions other then brief identification of the chemicals and became a Professor of Biochemistry & Molecular Biology at the most of my experiments were

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