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A Thesis Submitted for the Degree of PhD at the University of Warwick Permanent WRAP URL: http://wrap.warwick.ac.uk/108830 Copyright and reuse: This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications The Application of Biotransformations to the Synthesis of Partially Protected Sugar Derivatives. B y David A. Chaplin Submitted for the degree of Doctor of Philosophy Department of Chemistry University of Warwick January 1991. THE BRITISH LIBRARY D O C U M EN T SUPPLY CENTRE BRITISH THESES NOTICE The quality of this reproduction is heavily dependent upon the quality of the original thesis submitted for microfilming. 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List of figures: vii L ist of tables: xi D eclaration xii A ck n o w led g em en ts xiii S u m m a ry xiv List of abbreviations: xv Chapter One: Introduction. 1 .1 : The properties of sugar derivatives. 1 1 .2 : Sweetness and chloro-sugars. 3 1 .3 : Selectivity in the synthesis of sugar derivatives. 8 1 .4 : Chemical deprotection. 9 1 .5 : Acyl migration. 12 1 .6 : Enzymatic deacylations. 16 1 .7 : Enzymatic acylations. 27 1 .8 : Analysis. 38 Chapter Two: The Analysis of Sugar Mixtures. 2 .1 : Introduction. 47 2 .2 : The development of a method of analysis. 49 2 .3 : The analysis of perdeuterioacetylated mixtures. 51 2 .4 : Analysis of perdeuterioacetylated samples by n.m.r. 52 2 .5 : The analysis of perdeuterioacetylated samples by mass spectrometry. 56 2 .6 : The combination of both techniques to analyse samples. 61 iii 2.7: Analysis of a deacetylation reaction in greater detail: The deacetylation of glucose pentaacetate. 69 2.7.1: Analysis of the tetraacetate fraction. 80 2.7.2: Analysis of the triacetate fraction. 82 2.7.3: Analysis of the diacetate fraction. 85 2.7.4: Results. 86 2.8: Deacetylation of sucrose octaacetate using yeast esterase. 96 2.8.1: Analysis of the heptaacetate class. 101 2.8.2: Analysis of the hexaacetates. 103 2.8.3: Analysis of the pentaacetates. 105 2.8.4: Analysis of the tetraacetates. 107 2.8.5: Analysis of the triacetate class. 108 2.8.6: Discussion. 110 Chapter Three: The Synthesis of N-Acetyl-D- ' galactosamine. 3 .1 : Introduction. 116 3.2: The synthesis of the protected intermediate. 119 3.3: Inversion of configuration at C-4. 122 Chapter Four: Experimental Details. 4.1: General. 133 4.2: The hydrolysis of sucrose octaacetate catalysed by yeast esterase. 134 iv 4.2.1: The hydrolysis of a suspension of sucrose octaacetate catalysed by yeast esterase. 134 4.2.2: The hydrolysis of a solution of sucrose octaacetate using yeast esterase. 135 4.3: The Deacetylation of Glucose Derivatives. 135 4.3.1: a- and P-methyl-D-glucopyranoside tetraacetates. 135 4.3.2: The enzymatic hydrolysis of methyl-a-D- glucopyranoside tetraacetate catalysed by A. niger lipase. 136 4.3.3: Control experiments carried out on the hydrolysis of methyl-D-glucopyranoside. 137 4.3.3a: A study on the effect of the enzyme. 137 4.3.3b: A study of the effect of the enzyme on the free sugar. 137 4.3.3c: A study of the other anomer of methyl-D- glucopyranoside. 138 4.3.4: The hydrolysis of P-D-glucose pentaacetate. 138 4.3.4a: Separation of partly acetylated products. 139 4.4: The deacetylation of sucrose octaacetate catalysed by wheat germ lipase. 140 4.4.1: Small scale hydrolysis of sucrose octaacetate catalysed by wheat germ lipase. 140 4.4.2: Large scale hydrolysis of sucrose octaacetate catalysed by wheat germ lipase. 140 4.5: The Synthesis of 2-Acetamido-2-deoxy-a-D- galactopyranose. 141 v Appendix I: The study of sucrose acetates by n.m.r. spectroscopy. 149 Appendix 2. Sucrose Acylations. 152 Appendix 3: Data from the analysis of the deacetylation ex p e rim e n ts. 154 References. 161 vi List of Figures. Fig. 1.1: The structures of some common sweeteners. 2 Fig. 1.2: The postulated AH, B system for sweet taste. 4 Fig. 1.3: Superpositioning of D- and L-asparagine over the same AH,B,X receptor site showing the effect of stereochemistry. 5 Fig. 1.4: The AH,B,X tripartite system proposed by Kier. 6 Fig. 1.5: The two glucophores of l',4,6'-trichloro- 1 ',4t6’-trideoxy-ga/ac/i>-sucrose. 7 Fig. 1.6: The structure of sucrose octaacetate. 9 Fig. 1.7: Acyl migration via an ortho-acid intermediate. 13 Fig. 1.8: The C-4 to C-6 acyl migration. 14 Fig. 1.9: Migration of an acyl group from nitrogen to oxygen. 14 Fig. 1.10: The stucture of glucose pentaacetate. 20 Fig. 1.11: 1,2-3,4-diisopropylidene-a-D-glucopyranose and 1,2-5,6-diisopropylidene-a-D-glucofuranose. 22 Fig. 1.12: Sucrose octaacetate. 23 Fig. 1.13: The Michaelis-Menten mechanism. 29 Fig. 2.1: The products from the deacetylation of glucose pentaacetate. 49 Fig. 2.2: The eight acetate signals in the !H n.m.r. spectrum of sucrose octaacetate recorded in ds-pyridine/d6-benzene (1:1). 53 Fig. 2.3: The acetate region of the *H n.m.r. spectrum of a perdeuterioacetylated mixture of sucrose acetates. 54 Fig. 2.4: The !H n.m.r. spectra of sucrose octaacetate and a perdeuterioacetylated derivative. 55 vii Fig. 2.5: The mass spectrum of a sucrose pentaacetate class after perdeuterioacetylation. 57 Fig. 2.6: The mass spectrum of a perdeuterioacetylated mixture of sucrose acetates. 58 Fig. 2.7: The initial fragmentation of glucose pentaacetate. 59 Fig. 2.8: The initial fragmentation of sucrose octaacetate. 60 Fig. 2.9: The structure of sucrose octaacetate. 63 Fig. 2.10: The relative rates of hydrolysis of the acetate groups of sucrose octaacetate, catalysed by yeast esterase. 64 Fig. 2.11: The hydrolysis of sucrose octaacetate. 66 Fig. 2.12: The relative proportions of the heptaacetate and hexaacetate classes. 67 Fig.2.13: The relative proportion of the pentaacetate and tetraacetate classes. 67 Fig. 2.14: The structure of glucose pentaacetate. 70 Fig. 2.15: The anomerisation of glucose derivatives. 71 Fig. 2.16: Methyl-a-D-glucopyranoside. 72 Fig. 2.17: The acetate region of the *H n.m.r. spectrum of glucose pentaacetate, showing the ten resolved acetate signals, recorded in a 7:6 mixture of ^ 5-pyridine and d6-benzene. 74 Fig. 2.18a: The 2-D shift correlation spectra used to identify the individual acetate signals. 75 viii Fig. 2.18b: An expansion of the acetate region of the 2-D shift correlation spectra used to identify the individual acetate signals. 76 Fig. 2.19: The mass spectrum of a mixture of glucose acetates after perdeuterioacetylation. 78 Fig. 2.20: The acetate region of the 'H n.m.r. spectrum of a perdeuterioacetylated mixture of glucose acetates. 79 Fig. 2.21: The composition of the mixture by acetate class, for the deacetylation of glucose pentaacetate catalysed by lipase A. 87 Fig. 2.22: The major tetraacetate: 2,3,4,6-tetra-O- acetyl-D -glucose. 89 Fig. 2.23: The composition of the tetraacetate class. 90 Fig. 2.24: The major triacetate: 2,4,6-tri-O-acetyl- D-glucose. 91 Fig. 2.25: The composition of the triacetate class. 91 Fig. 2.26: The composition of the diacetate class. 93 Fig. 2.27: The relative amounts of the monoacetate and of glucose. 94 Fig. 2.28: Sucrose octaacetate. 97 Fig. 2.29: The class composition of the mixture from the small scale deacetylation of sucrose octaacetate catalysed by wheat germ lipase. 98 Fig. 2.30: The class composition of the large scale d ea cety latio n . 100 Fig. 2.31: The composition of the heptaacetate class. 103 Fig. 2.32: The composition of the hexaacetate class. 105 Fig. 2.33: The composition of the pentaacetate class. 106 ix Fig. 2.34: The composition of the tetraacetate class. 108 Fig. 2.35: The composition of the triacetate class. 109 Fig. 2.36: The relative amounts of the diacetate class, monoacetate class and sucrose in the reaction m ix tu re. 110 Fig. 2.37: The major heptaacetate: r,2,3,3',4,4',6-hepta- O -acetyl sucrose. Ill Fig. 2.38: The major hexaacetate: 1',2,3,3',4,6-hexa- O -acetyl sucrose. 112 Fig. 2.39: The major pentaacetate: 2,3,3',4,6-penta- O -acetyl sucrose. 112 Fig. 2.40: The two major tetraacetates: (a) 2,3,3',6- and (b) 3,3',4,6-tetra-O-acetyl sucrose.