{"id":20601,"date":"2019-04-01T16:12:35","date_gmt":"2019-04-01T15:12:35","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=20601"},"modified":"2019-04-29T17:10:39","modified_gmt":"2019-04-29T16:10:39","slug":"impossible-molecules","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20601","title":{"rendered":"Impossible molecules."},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"20601\">\n<p>Members of the chemical FAIR data community have just met in Orlando (with help from the <a href=\"https:\/\/iupac.org\/event\/fair-publishing-guidelines-for-spectral-data-and-chemical-structures\/\" target=\"_blank\" rel=\"noopener noreferrer\">NSF, the American National Science Foundation<\/a>)\u00a0to discuss how such data is progressing in chemistry. There are a lot of themes converging at the moment. Thus this article<span id=\"cite_ITEM-20601-0\" name=\"citation\"><a href=\"#ITEM-20601-0\">[1]<\/a><\/span> extolls the virtues of having raw NMR data available in natural product research, to which we added that such raw data should also be made<strong> FAIR<\/strong> (Findable, Accessible, Interoperable and Reusable) by virtue of adding rich metadata and then properly registering it so that it can be searched. These themes are combined in another article which made a recent appearance.<span id=\"cite_ITEM-20601-1\" name=\"citation\"><a href=\"#ITEM-20601-1\">[2]<\/a><\/span><\/p>\n<p>One of the speakers made a very persuasive case based in part on <em>e.g.<\/em> the following three molecules which are discussed in the first article<span id=\"cite_ITEM-20601-0\" name=\"citation\"><a href=\"#ITEM-20601-0\">[1]<\/a><\/span> (the compound numbers are taken from there). The question was posed at our meeting: <strong><em>why<\/em><em>\u00a0did the referees not query these structures<\/em><\/strong>? And the answer in part is to provide referees with access to the full\/primary\/raw NMR data (which almost invariably they currently do not have) to help them check on the peaks, the purity and indeed the assignments. I am sure tools that do this automatically from such supplied data by machines on a routine basis do exist in industry (and which is something FAIR is designed to enable). Perhaps there are open source versions available?<\/p>\n<table border=\"1\">\n<tbody>\n<tr>\n<th>17<\/th>\n<th>18<\/th>\n<th>19<\/th>\n<\/tr>\n<tr>\n<td><a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/17.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-20602\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/17.svg\" alt=\"\" width=\"100\" \/><\/a><br \/>\n\u00a0<\/td>\n<td><a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/18.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-20603\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/18.svg\" alt=\"\" width=\"100\" \/><\/a><\/td>\n<td><a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/19.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-20604\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/19.svg\" alt=\"\" width=\"250\" \/><\/a><\/td>\n<\/tr>\n<tr>\n<td>328<span id=\"cite_ITEM-20601-2\" name=\"citation\"><a href=\"#ITEM-20601-2\">[3]<\/a><\/span><\/td>\n<td>348<\/td>\n<td>713<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Here I suggest a particularly simple and rapid &#8220;reality check&#8221; which I occasionally use myself. This is to compute the <em>steric energy<\/em> of the molecule using molecular mechanics. The mechanics method is basically a summation of simple terms such as the bond length, bond angle, torsion angle, a term which models non bonded repulsions, dispersion attractions and electrostatic contributions. The first three are close to zero for an unstrained molecule (by definition). The last three terms can be negative or positive, but unless the molecule is protein sized, they also do not depart far from zero. A suitable free tool that packages all this up is <a href=\"https:\/\/avogadro.cc\">Avogadro<\/a>.<\/p>\n<p>The procedure is as follows<\/p>\n<ol>\n<li>Start from the Chemdraw representation of the molecule. If the publishing authors have been FAIR, you might be able to acquire that from their deposited data. Otherwise, redraw it yourself and save as <em>e.g.<\/em> a molfile or Chemdraw .cdxml file.<\/li>\n<li>Drop into Avogadro, which will build a 3D model for you using stereochemical information present in the Chemdraw or Molfile.<\/li>\n<li>In the <strong>\u00a0E<\/strong> tool (at the top on the left of the Avogadro menu) select <em>e.g.<\/em> the MMFF94 force field. This is a good one to use for &#8220;organic&#8221; molecules for which the total steric energy for &#8220;normal&#8221; molecules is likely to be &lt; 200 kJ. Calculate that for your system; this normally takes less than one minute to complete. The values obtained for the three above are shown in the table. All three are well over 200 kJ\/mol, which should set alarm bells ringing.<\/li>\n<li>A &#8220;more reasonable&#8221; structure for <strong>17<\/strong> is shown below. This has a steric energy of 152 kJ\/mol, some 176 kJ\/mol lower than the original structure. This does not of itself &#8220;prove&#8221; this alternative, but it is a starting point for showing it might be correct.<a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/17-correct1.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-20615\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/17-correct1.svg\" alt=\"\" width=\"150\" \/><\/a>Of course mis-assigned but otherwise reasonable structures are unlikely to be revealed by the steric energy test. But impossible ones will probably always be flagged as such using this procedure.\u00a0<\/li>\n<\/ol>\n<hr \/>\n<p><b>Postscript<\/b>: Hot on the heels of writing this, the molecule <b>Populusone<\/b> came to my attention.<span id=\"cite_ITEM-20601-3\" name=\"citation\"><a href=\"#ITEM-20601-3\">[4]<\/a><\/span> On first sight, it seems to have some of the attributes of an &#8220;impossible molecule&#8221; (click on diagram below for 3D coordinates).<br \/>\n<img decoding=\"async\" onclick=\"jmolApplet([450,450],'load wp-content\/uploads\/2019\/04\/Popusulin.mol;spin 3;','c2');\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/04\/liukaixin_384.svg\" alt=\"\" class=\"aligncenter size-full wp-image-20631\" width=\"300\"\/><br \/>\nHowever, it has been fully characterised by x-ray analysis! The steric energy using the method above comes out at 384 kJ\/mol, which in the region of impossibility! This can be decomposed into the following components: bond stretch 30, bend 51, torsion 32, van der Waals (including repulsions) 177, electrostatics 87 (+ some minor cross terms). These are fairly evenly distributed, with internal steric repulsions clearly the largest contributor. The C=C double bond is hardly distorted however, which is in its favour. Clearly a natural product can indeed load up the unfavourable interactions, and this one must be close to the record of the most intrinsically unstable natural product known!<\/p>\n<h2>References<\/h2>\n    <ol class=\"kcite-bibliography csl-bib-body\"><li id=\"ITEM-20601-0\">J.B. McAlpine, S. Chen, A. Kutateladze, J.B. MacMillan, G. Appendino, A. Barison, M.A. Beniddir, M.W. Biavatti, S. Bluml, A. Boufridi, M.S. Butler, R.J. Capon, Y.H. Choi, D. Coppage, P. Crews, M.T. Crimmins, M. Csete, P. Dewapriya, J.M. Egan, M.J. Garson, G. Genta-Jouve, W.H. Gerwick, H. Gross, M.K. Harper, P. Hermanto, J.M. Hook, L. Hunter, D. Jeannerat, N. Ji, T.A. Johnson, D.G.I. Kingston, H. Koshino, H. Lee, G. Lewin, J. Li, R.G. Linington, M. Liu, K.L. McPhail, T.F. Molinski, B.S. Moore, J. Nam, R.P. Neupane, M. Niemitz, J. Nuzillard, N.H. Oberlies, F.M.M. Ocampos, G. Pan, R.J. Quinn, D.S. Reddy, J. Renault, J. Rivera-Ch\u00e1vez, W. Robien, C.M. Saunders, T.J. Schmidt, C. Seger, B. Shen, C. Steinbeck, H. Stuppner, S. Sturm, O. Taglialatela-Scafati, D.J. Tantillo, R. Verpoorte, B. Wang, C.M. Williams, P.G. Williams, J. Wist, J. Yue, C. Zhang, Z. Xu, C. Simmler, D.C. Lankin, J. Bisson, and G.F. Pauli, \"The value of universally available raw NMR data for transparency, reproducibility, and integrity in natural product research\", <i>Natural Product Reports<\/i>, vol. 36, pp. 35-107, 2019. <a href=\"https:\/\/doi.org\/10.1039\/c7np00064b\">https:\/\/doi.org\/10.1039\/c7np00064b<\/a>\n\n<\/li>\n<li id=\"ITEM-20601-1\">A. Barba, S. Dominguez, C. Cobas, D.P. Martinsen, C. Romain, H.S. Rzepa, and F. Seoane, \"Workflows Allowing Creation of Journal Article Supporting Information and Findable, Accessible, Interoperable, and Reusable (FAIR)-Enabled Publication of Spectroscopic Data\", <i>ACS Omega<\/i>, vol. 4, pp. 3280-3286, 2019. <a href=\"https:\/\/doi.org\/10.1021\/acsomega.8b03005\">https:\/\/doi.org\/10.1021\/acsomega.8b03005<\/a>\n\n<\/li>\n<li id=\"ITEM-20601-2\">A.I. Savchenko, and C.M. Williams, \"The Anti\u2010Bredt Red Flag! Reassignment of Neoveratrenone\", <i>European Journal of Organic Chemistry<\/i>, vol. 2013, pp. 7263-7265, 2013. <a href=\"https:\/\/doi.org\/10.1002\/ejoc.201301308\">https:\/\/doi.org\/10.1002\/ejoc.201301308<\/a>\n\n<\/li>\n<li id=\"ITEM-20601-3\">K. Liu, Y. Zhu, Y. Yan, Y. Zeng, Y. Jiao, F. Qin, J. Liu, Y. Zhang, and Y. Cheng, \"Discovery of Populusone, a Skeletal Stimulator of Umbilical Cord Mesenchymal Stem Cells from &lt;i&gt;Populus euphratica&lt;\/i&gt; Exudates\", <i>Organic Letters<\/i>, vol. 21, pp. 1837-1840, 2019. <a href=\"https:\/\/doi.org\/10.1021\/acs.orglett.9b00423\">https:\/\/doi.org\/10.1021\/acs.orglett.9b00423<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> <!-- kcite-section 20601 -->","protected":false},"excerpt":{"rendered":"<p>Members of the chemical FAIR data community have just met in Orlando (with help from the NSF, the American National Science Foundation)\u00a0to discuss how such data is progressing in chemistry. There are a lot of themes converging at the moment. Thus this article extolls the virtues of having raw NMR data available in natural product [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[2],"tags":[2535,1655,2606,27,1395,2537,2539,2605,1959,1630,2533,231,2506,2607,1442,2505,1512,2534,1560,2536,2540,2604,2538,2541,42],"ppma_author":[2661],"class_list":["post-20601","post","type-post","status-publish","format-standard","hentry","category-chemical-it","tag-american-national-science-foundation","tag-bond-length","tag-chemdraw","tag-chemical","tag-chemistry","tag-city-orlando","tag-company-nsf","tag-force-field","tag-intermolecular-forces","tag-molecular-geometry","tag-national-science-foundation","tag-natural-product","tag-natural-sciences","tag-orlando","tag-physical-organic-chemistry","tag-physical-sciences","tag-quantum-chemistry","tag-science-and-technology-in-the-united-states","tag-stereochemistry","tag-steric-energy","tag-steric-energy-test","tag-strain","tag-suitable-free-tool","tag-unstable-natural-product","tag-x-ray"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Impossible molecules. - Henry Rzepa&#039;s Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20601\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Impossible molecules. - Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"og:description\" content=\"Members of the chemical FAIR data community have just met in Orlando (with help from the NSF, the American National Science Foundation)\u00a0to discuss how such data is progressing in chemistry. 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Part of the problem perhaps is that many of the current reward systems for scientists do not always help promote\u2026","rel":"","context":"In &quot;Bradley-Mason Prize for Open Chemistry&quot;","block_context":{"text":"Bradley-Mason Prize for Open Chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2131"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":16721,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16721","url_meta":{"origin":20601,"position":2},"title":"Molecule orbitals as indicators of reactivity: bromoallene.","author":"Henry Rzepa","date":"September 1, 2016","format":false,"excerpt":"Bromoallene is a pretty simple molecule, with two non-equivalent double bonds. How might it react with an electrophile, say dimethyldioxirane (DMDO) to form an epoxide? Here I explore the difference between two different and very simple approaches to predicting its reactivity. Both approaches rely on the properties of the reactant\u2026","rel":"","context":"In &quot;reaction mechanism&quot;","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"KS1","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/08\/KS1.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":20342,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20342","url_meta":{"origin":20601,"position":3},"title":"Open Access journal publishing debates &#8211; the elephant in the room?","author":"Henry Rzepa","date":"November 4, 2018","format":false,"excerpt":"For perhaps ten years now, the future of scientific publishing has been hotly debated. The traditional models are often thought to be badly broken, although convergence to a consensus of what a better model should be is not apparently close. But to my mind, much of this debate seems to\u2026","rel":"","context":"In &quot;Chemical IT&quot;","block_context":{"text":"Chemical IT","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":18318,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18318","url_meta":{"origin":20601,"position":4},"title":"Conference report: OPEN SCIENCE AND THE CHEMISTRY LAB  OF THE FUTURE","author":"Henry Rzepa","date":"May 23, 2017","format":false,"excerpt":"This is taking place in the idyllic surroundings of the Niederwald forest, R\u00fcdesheim, Germany. Here I highlight only aspects of the first three talks. Martin Hicks introduced the conference with concepts such as the global public good. In the area of open access, he reminded us of the terms Platinum\/Diamond\u2026","rel":"","context":"In &quot;Chemical IT&quot;","block_context":{"text":"Chemical IT","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/05\/IMG_1672.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/05\/IMG_1672.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/05\/IMG_1672.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":15048,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=15048","url_meta":{"origin":20601,"position":5},"title":"I&#8217;ve started so I&#8217;ll finish. The mechanism of diazo coupling to indoles &#8211; forty (three) years on!","author":"Henry Rzepa","date":"December 24, 2015","format":false,"excerpt":"The BBC TV quiz series Mastermind\u00a0was first broadcast in the UK in 1972,\u00a0the same time\u00a0I was starting to investigate\u00a0the mechanism of diazocoupling to substituted indoles as part of my Ph.D. researches. The BBC program became known\u00a0for the\u00a0catch phrase\u00a0I've started so I'll finish;\u00a0here I will try to follow this precept with\u2026","rel":"","context":"In &quot;Historical&quot;","block_context":{"text":"Historical","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=565"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20601","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=20601"}],"version-history":[{"count":16,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20601\/revisions"}],"predecessor-version":[{"id":20881,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20601\/revisions\/20881"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=20601"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=20601"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=20601"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=20601"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}