The Allure of Mass Spectrometry: from an Earlyday Chemist’S Perspective
Total Page：16
File Type：pdf, Size：1020Kb
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 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mas.21499 This reminiscing review article is an account of the author’s I. INTRODUCTION fascination and involvements with mass spectrometry from the perspective of an organic chemist with an interest in natural By professional training I am an organic chemist with a long product chemistry. It covers a period from 1961 through the mid standing fascination with natural product chemistry, probing the 1990s as mass spectrometry evolved form a novelty technique to chemical bounties and mysteries of Mother Nature. Synthetic become a most widely used analytical technique. Following a organic chemistry and natural product chemistry share a brief synopsis of my pathway to mass spectrometry, my research fundamental need for structural elucidations. In the late 1950s efforts in this field are presented with a focus mainly on evolving and at the beginning of the 1960s there were only a limited principles and technologies which I had personal involvements number of readily available analytical tools for structure with. To provide historical perspectives, discussions of these identifications. These included IR and UV spectroscopy, developments are accompanied by brief outlines of the relevant combustion-based elemental analyses and for configurational state-of-the-art, shedding light on the technical and conceptual studies optical rotation, optical rotatory dispersion (ORD) and challenges encountered during those early days in mass circular dichroism (CD). NMR spectroscopy was in baby shoes spectrometry. Examples are presented of my involvements with with the introduction of the first commercial 60 MHz instru- basic and applied research in mass spectrometry during gradu- ments by Varian, Palo Alto, CA in 1961. The low sensitivity of ate studies at Stanford University and close to three decade these NMR instruments, requiring 20 mg or more samples for a tenure in pharmaceutical research at Syntex Research. My basic meaningful analysis, prevented their application to samples research interests focused mainly on principles of electron available only from small scale preparations. NMR gained ionization induced fragmentation mechanisms, with an empha- widespread use later in the 1960s with the introduction of the sis on steroids and other model compounds. Extensive deuterium 100 MHz and Fourier Transform (FT) instruments which labeling evidence was used to determine the fragmentation reduced the sample requirement by ten fold and provided far mechanisms of the diagnostically significant ions in the spectra more structural information. of numerous model compounds, uncovering examples of wide- In search for new analytical methods, attention turned to ranging hydrogen transfers, skeletal rearrangements, methyl mass spectrometry (MS) as a technique with potentials to and phenyl migrations, stereoselective fragmentations and low provide a wealth of structural information on sub-milligram and high energy fragmentation processes. Depiction of the amount of samples. Mass spectrometry had been in use already industrial research phase of my career includes comments on during and after the Second World War in the petroleum industry the pivotal role mass spectrometry played on advancing modern to analyze volatile hydrocarbons. In the 1950s a select group of pharmaceutical research. Examples are presented of involve- pioneering investigators experimented with its application to ments with instrumental developments and a few select cases of non-petrochemical, lower volatility compounds demonstrating applied research, including studies of bile mechanisms in its potential usefulness in general organic chemistry. Their vertebrates, identification of bisphenol-A leaching from steril- reports were impressive and by the time I started my graduate ized polycarbonate containers, high sensitivity TCDD analyses studies in 1961 mass spectrometry was already considered an and other projects. Reflecting on my services for the mass exciting new technique with great potentials for becoming a spectrometry society, involvements with the co-founding and major analytical tool for structural elucidations. In this review I 12 year chairing of the Asilomar Conference on Mass Spectrom- intend to show how I succumbed to this appeal and how mass etry and founding of the Bay Area Mass Spectrometry regional spectrometry became my career long scientific interest. MS discussion group, as part of my services for the mass My involvement in this field spans the period from mass spectrometry community, are presented in some detail. # 2016 spectrometry being the domain of mostly spectroscopists, Wiley Periodicals, Inc. Mass Spec Rev physicists and geochemists, through its evolution to become a most widely used analytical technique with current applications Keywords: steroids; stable isotope labeling; fragmentation in virtually every scientific and medical field. This review mechanisms; stereospecific fragmentation; bile steroids; TCDD; focuses on developments in organic chemistry applications bisphenol-A; instrumental developments; Asilomar Conference which I had personal involvements with, including comments on on Mass Spectrometry; Bay Area Mass Spectrometry their relevance to the contemporary state-of-the-art. A brief overview of some of my research contributions in this field is presented, concentrating more on conceptual descriptions rather than technical details, followed by examples of applications of mass spectrometry in the pharmaceutical industry and the role ÃCorrespondence to: 4133 Thain Way, Palo Alto 94306, CA. this technique played in the advancement of modern pharmaceu- E-mail: [email protected] tical research. Mass Spectrometry Reviews # 2016 by The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc. & TOK} ES During the second half of the 20th century, exponential freedom of the press and other issues which were delineated in a growth in the use and instrumental developments in mass ten point declaration. I left work in a hurry and headed to the spectrometry created a rapidly growing scientific community Parliament where I witnessed what had become the start of the dedicated to this field. My contributions to the professionalism 1956 Hungarian Revolution against the Soviet occupation. That of this emerging society are outlined in Section V. Two was the last day I set foot in Chinoin as an employee. contributions with lasting consequence for the society, the co- After a brief period of gaining freedom, on November 4 the founding and 12 year chairing of the Asilomar Conference on revolution was brutally crushed by the invading Soviet Army. Mass Spectrometry, an international research conference series, Due to concerns for my safety in Budapest and the obvious and involvements with the founding of Bay Area Mass return of political repression in the country, on December 26 I Spectrometry, a regional MS discussion group, are discussed in decided to join the exodus of some two hundred thousand some detail in Sections V(A) and V(B). refugees from Hungary with the then living members of my family—mother, younger brother and an older cousin. After an II. PATHWAY TO MASS SPECTROMETRY all night march in pitch dark, through deep-plowed fields covered with two feet of snow, and dodging the occasional Sharing an incident commonly mentioned in the autobiogra- search lights and wildly shooting inebriated Russian border phies of many noted scientists who were born in the first half of patrols by hiding in the snow, we were fortunate to make it to the 20th century, and so eloquently depicted by Oliver Sacks in Austria on our first trial—bloodied by frost bites but free at last. his epic biographical book, “Uncle Tungsten; Memories of a We stayed in Austria for 6 months in refugee camps but by this Chemical Boyhood” (Sacks, 2001), I too got interested in time the US quota for Hungarian immigrants was already full. chemistry by having received a chemistry kit at age 11. In 1948, However, with the aid of an affidavit from a distant relative in the war ravaged city of Budapest, Hungary, this kit was living in California, and most probably by the insistence of my prepared by an entrepreneurial young man who had a complete brother and I that we wanted to attend university in the USA, in disregard, or lack of comprehension, of safety considerations. It June 1957 we were allowed to immigrate to the US as a “family came with no instructions other then brief identification of the consolidation” case. My brother, Zoltan A. Tok} es, in time chemicals and most of my experiments were based on trial-and- became a Professor of Biochemistry & Molecular Biology at the error, or by following often boisterous suggestions of other kids Keck School of Medicine, University of Southern California in who learned the means of creating visual, audio or olfactory Los Angeles. With his and my modest contributions to science effects. This was an opportunity for exciting experimentations we did our best to compensate our adapted home country for the with “chemistry in the raw” and, of course, led to frequent opportunities provided to us. disapprovals by our household members. However, these early Within days after our arrival in California I landed a experimentations and the sharing of excitements with like- janitorial job at the Queen of Angels Hospital in Los