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Chemoenzymatic Resolution of Selected Vicinal Diols Faculty of Natural Resources School of Business and Natural Science Universi

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Chemoenzymatic Resolution of Selected Vicinal Diols Faculty of Natural Resources School of Business and Natural Science Universi Viðskipta- og Raunvísindasvið Auðlindadeild 2014 Chemoenzymatic resolution of selected vicinal diols Sean Michael Scully Final Project in Biotechnology Faculty of Natural Resources School of Business and Natural Science University of Akureyri 2014 ii Háskólinn á Akureyri Viðskipta- og Raunvísindasvið Viðskipta- og Raunvísindasvið Auðlindadeild Námskeið LOK 1123 og LOK 1223 Heiti verkefnis Chemoenzymatic resolution of selected vicinal diols Verktími August 2011 – April 2014 Nemandi Sean Michael Scully Leiðbeinandi Sigþór Pétursson, PhD Upplag Blaðsíðufjöldi 104 Fjöldi viðauka Útgáfu- og notkunarréttur Fylgigögn ISSN-númer Lokaverkefni til 90 eininga B.Sc.-prófs á líftæknibraut iii I hereby attest that I am the author of this dissertation herein and that it is a product of my own academic research from the autumn of 2012 to the spring of 2014. Sean Michael Scully Signature, date and place I hereby certify that the dissertation successfully fulfills the requirements to complete a Bachelor of Science in Biotechnology at the University of Akureyri. Signature, date and place ii Abstract The use of chemoenzymatic resolutions for the separation of racemic mixtures is a common route that affords enantiomerically pure compounds. Finding novel and selective protecting group strategies to facilitate the resolution of 1,2-diol systems remains challenging. The use of tin(II) halide-catalyzed reactions with diazo[bis(4- methylphenyl)]methane with racemic vicinal 1,2-diols gives a mixture of the corresponding 1- and 2-benzhydryl ethers with a regiopreference for the primary hydroxyl group in good overall yield. Tin(II) chloride and Tin(II) bromide were evaluated as catalyst for the regioselective introduction of bis(4-methylphenyl)methane ethers from the corresponding diazocompound. Following partial protection, five commercially available lipases were evaluated for their ability to resolve 1-benzhydryl ethers of 1,2-diol systems. Subsequent kinetic resolution with immobilized lipase from Pseudomonas cepacia afforded the corresponding (2R) acetate and (2S) alcohol. De-acylation of the 2R diol affords the corresponding free alcohol. Keywords: Biocatalysis, lipase, kinetic resolution, 1,2-diols, tin(II) halides, stereochemistry . iii Háskólinn á Akureyri Viðskipta- og Raunvísindasvið Acknowledgements This work was carried out at the University of Akureyri. I would like to thank Dr. Sigríður Jónsdóttir for her assistance with obtaining NMR and MS data over the past 4 years. I would also like to kindly think Eva María Ingvadóttir for her helpful comments regarding this manuscript. I would like to express my deep and eternal gratitude to Dr. Sigþór Pétursson for opening the door for the continuation of my career in the physical sciences in 2005 and helping me restart my career in science in 2008. I would also like to extend my gratitude to my lovely wife, Hugrún, for her nearly unlimited patience with my work and academic habits over the past seven years. The finalization of this manuscript would not have been possible without her support, dedication and a willingness to overlook my continued absence. „I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.“ Sir Issac Newton iv Háskólinn á Akureyri Viðskipta- og Raunvísindasvið Útdráttur Aðskilnaður handhverfa með efnafræðilegum aðferðum og notkun ensíma eru vel þekktar aðferðir við einangrun hreinna handhverfa. Dæmi um slíkar handhverfur eru 1,2-diol, sem innihalda hendið kolefni, og afleiður þeirra. Staðvendin myndun eter afleiða af eingreindum alkohól hóp slíkra díóla, sérstaklega með stórum alkyl hópum, hentar vel fyrir myndun afleiða fyrir ensím hvörfin. Tin(II) halíð hvata hvörf diaryldiazometan efnasambanda við hliðlæg díól og mynda eingöngu einetera þar sem eingreindi eterinn myndast í meira magni. Heildarheimtur einetranna eru góðar. Samanburður var gerður á tin(II) klóríði og tin(II) brómíði sem hvata fyrir myndun bis(4-methylphenyl)methyl etera með notkun tilheyrandi diazoefnsambands. Eftir einangrun eingreinda etersins, voru fimm aðkeyptir lípasar rannsakaðir við aðskilnað handhverfa þessara 1-diarylmethyl etera díólanna. Lípasinn frá Pseudomonas cepacia var síðan notaður við myndun (2R)-asetatsins sem var skilið frá (2S)-alkohólinu. Afasetylerun (2R)-asetatsins gaf síðan (2R)-alkohólið. v Háskólinn á Akureyri Viðskipta- og Raunvísindasvið Table of Contents Abstract .................................................................................................................................... iii Acknowledgements ................................................................................................................... iv Útdráttur ..................................................................................................................................... v List of Figures ........................................................................................................................... ix List of Tables ............................................................................................................................ xi Abbreviations ........................................................................................................................... xii 1 Background and Research Objectives .................................................................................... 1 1.1 Stereochemistry................................................................................................................ 2 1.1.1 Basic terminology in stereochemistry ....................................................................... 4 1.1.2 Nomenclature of stereoisomers ................................................................................. 5 1.1.3 Metrics in Stereochemistry ....................................................................................... 9 1.1.4 Asymmetric strategies in synthesis ......................................................................... 11 1.2 Biocatalysis with lipases ................................................................................................ 13 1.2.1 General Aspects of Biocatalysis ............................................................................. 14 1.2.2 Lipases .................................................................................................................... 16 1.2.3 Biocatalytic routes to enantiomerically pure diols .................................................. 29 1.3 Benzhydryl Derivatives as Protecting Groups ............................................................... 33 1.3.1 Overview of Protecting Group Strategy for Hydroxyl Groups ............................... 33 1.3.2 Benzhydryl Ethers as Hydroxyl Protecting Groups ................................................ 36 2 Experimental ......................................................................................................................... 41 2.1 General methods ............................................................................................................ 41 2.2 Preparation of diazo compounds .................................................................................... 43 2.2.1 Preparation of diazo[bis(4-methylphenyl)]methane ............................................... 43 2.2.2 Preparation of diazo[bis(4-methoxyphenyl)]methane ............................................ 43 2.3 Protection studies towards primary benzhydrylation of vicinal diols ............................ 44 2.3.1 Benzhydralation experiments on 1,2-propanediol .................................................. 44 vi Háskólinn á Akureyri Viðskipta- og Raunvísindasvið rac-[1-O-bis(4-methylphenyl)methyl]–propan-2-ol (SnCl2 catalyzed) ....................... 44 rac-[1-O-bis(4-methylphenyl)methyl]–propan-2-ol (SnBr2 catalyzed) ....................... 45 2.3.2 Benzhydrylation experiments on 3-phenoxy-1,2-propanediol ............................... 47 3-O-phenoxy-1-O-(bis(4-methylphenyl)methyl)-propan-2-ol (SnCl2 catalyzed) ........ 47 3-O-phenoxy-1-O-(bis(4-methylphenyl)methyl)-propan-2-ol (SnBr2 catalyzed) ........ 47 Effort towards 1-O-bis(4-methoxyphenyl)dimethyldiphenyl –propan-2-ol (SnCl2 catalyzed) ..................................................................................................................... 48 Effort towards 1-O-bis(4-methoxyphenyl)dimethyldiphenyl –propan-2-ol (SnBr2 catalyzed) ..................................................................................................................... 48 2.3.3 Primary benzyhydrylation of 3-chloro-1,2-propanediol ......................................... 49 1-O-bis(4-methylphenyl)-3-chloro-propan-2-ol (SnCl2 catalyzed) ............................. 49 Separation of 1-dimethyldipheny 3-chloro-propane-2-ol ether from 2 ether (pg 40) .. 50 2.4 Lipase-catalyzed resolution of partially protected diols ................................................ 51 2.4.1 Comparison of lipases for 2(R) acetylation of rac-1[bis(4- methylphenyl)]methoxypropane-2-ol .............................................................................. 51 2.4.2 Kinetic Resolution of rac-1[bis(4-methylphenyl)]methoxypropane-2-ol .............. 52 2.4.3 Kinetic Resolution of 1-dimethyldiphenyl ether of rac-3-phenoxy-1[bis(4- methylphenyl)]methoxypropane-2-ol .............................................................................
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