Advances in the stereoselective synthesis of antifungal agents and ...

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Chapter 1 31Enantioselective syntheses and the separation of diasteroisomers wereinvestigated in greater detail as compared to the crystallization ofdiasteroisomeric salts.Synthesis and sepation of diasteroisomersEnantioselective SynthesisCHIRAL TARGETSClassical Resolution by Crystallization of Diastereoisomeric SaltFigure 1.17: Synthetic approaches to enantiopure compounds.The described work was focused on two different classes of drugs: (a)bifonazole 6a and its analogues (antifungal agents) and (b) the Menarinianticancer drug 18 (aromatase inhibitor) (Fig 1.18).NONRNN6a18R = Halides, CN,Me.Figure 1.18: Bifonazole 6a and Menarini anticancer drugs 18.Neither enantioselective syntheses nor general methods to obtain theseclasses of compounds in enantiopure form are reported in literature; withthe exception of a patent for Vorazole 17a 139 .
Chapter 1 32These apparently similar two classes of compounds showed acompletely different chemical behavior during our investigation as willbecome clear in the following chapters. Structurally quite simple, thesecompounds contain only one chiral centre in form of a tertiary carbonbound to three different aromatic substituents. The system is prone to formvery stable carbocations 143 under acidic conditions, furthermore themolecules do not posses any site of functionalization which would allow theformation of separable diasteroisomers. The following paragraphs will showthe consequences of these features on the employed general strategies.1.6.1. Approaches based on diasteroisomers.This approach consists in the synthesis of molecules having a"removable anchor" group, such as a carboxylic acid, amine or alcohol,that could be bound to another molecule with defined chirality in order toform a pair of diasteroisomers. The different physico-chemical propertiesof the diasteroisomers can be used to separate them by chromatography orby crystallization. After the separation it is necessary to remove the anchorgroup and to generate the molecule with the defined chiral centre under suchmild conditions as to avoid any possible racemization of the single isomerobtained from the separation. The last step is the removal of the anchorfrom the molecule to generate the free enantiomer of the drug. Again it isnecessary to find the mildest conditions in order to avoid racemizations ofthe final compouds (Fig. 1.20 ).Our target molecules are unfunctionalized and we have designed twodifferent functional groups to be introduced as anchors, either on thearomatic moieties or on the imidazole ring (Fig. 1.19).ArArRNNNN RAr= Biphenyl, Benzofurane R = NH 2 ,COOH,OH.Figure 1.19: Possible positions of anchor groups.
Page 1 and 2: Advances in the stereoselectivesynt
Page 3: ACKNOWLEDGMENT:I would like to than
Page 6 and 7: Summary:Numerous drugs are chiral,
Page 8 and 9: IndexII2.2 Synthesis of enantiopure
Page 10 and 11: IndexIV4.4. Stereochemical Assignme
Page 12 and 13: IndexVImethyl amine 69 1446.6. Stud
Page 14 and 15: IndexVIII8.23.3.1 Desilylation usin
Page 16 and 17: Chapter 1 11.Introduction1.1. Chira
Page 18 and 19: Chapter 1 3The concept of stereoche
Page 20 and 21: Chapter 1 5switches is in the area
Page 22 and 23: Chapter 1 7-bonds 9 . It is now wid
Page 24 and 25: Chapter 1 914CH 3Cyt P-450 DMOH3O 2
Page 26 and 27: Chapter 1 11piperazine) is also the
Page 28 and 29: Chapter 1 13The four stereoisomers
Page 30 and 31: Chapter 1 15single enantiomers and
Page 32 and 33: Chapter 1 17was synthesized by the
Page 34 and 35: Chapter 1 19HOHODesmolaseHOCholeste
Page 36 and 37: Chapter 1 21formic acid results in
Page 38 and 39: Chapter 1 23inactivation. 113 . Bec
Page 40 and 41: Chapter 1 25Two newer compounds whi
Page 42 and 43: Chapter 1 2715 is an advanced repre
Page 44 and 45: Chapter 1 29transformation of the a
Page 48 and 49: Chapter 1 33+R,S DRUG ANCHOR R MOLE
Page 50 and 51: Chapter 1 35solubilized in hot etha
Page 52 and 53: Chapter 2 37RsORmRmRsRLRL RRRLH - A
Page 54 and 55: Chapter 2 39The stereochemistry and
Page 56 and 57: Chapter 2 41An asymmetric reducing
Page 58 and 59: Chapter 2 43This approach clearly e
Page 60 and 61: Chapter 2 45PhaxeqP 1MP 2axeqPhP 2M
Page 62 and 63: Chapter 2 47pyrrolidine ] 20 , LAH-
Page 64 and 65: Chapter 2 49Enzymatic reactions are
Page 66 and 67: Chapter 2 51As [ES] in equation 4 c
Page 68 and 69: Chapter 2 53E+AK 1AK -1AEAK 2AE+PE+
Page 70 and 71: Chapter 2 552.2.4 Lipases.Most lipa
Page 72 and 73: Chapter 2 57enzyme intermediate can
Page 74 and 75: Chapter 2 59projecting above the pl
Page 76 and 77: Chapter 2 612.3.1.1. Step 1: Adduct
Page 78 and 79: Chapter 2 63A -+ ROHRO - + AH'RO 2
Page 80 and 81: Chapter 2 65There are various effec
Page 82 and 83: Chapter 2 67The reactions were foun
Page 84 and 85: Chapter 2 69Yamanaka and coworkers
Page 86 and 87: Chapter 2 71sodium or potassium car
Page 88 and 89: Chapter 3 73The reaction is quite s
Page 90 and 91: Chapter 3 75literature as the best
Page 92 and 93: Chapter 3 77dry solvents and, is ch
Page 94 and 95: Chapter 3 79XXOH+ H 2 NDry K 2 CO 3
Page 96 and 97:
Chapter 3 81substituents are the mo
Page 98 and 99:
Chapter 3 83induces a rotation of t
Page 100 and 101:
Chapter 3 85very sharp and it was p
Page 102 and 103:
Chapter 3 87Raney NickelOH Br MeOH;
Page 104 and 105:
Chapter 4 8933a-m were hydrolysed t
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Chapter 4 91benzo[b]furane (entries
Page 108 and 109:
Chapter 4 93hydroxy or amine groups
Page 110 and 111:
Chapter 4 95the products with ethyl
Page 112 and 113:
Chapter 4 97NCO 2 HNCO 2 H(±)34c(-
Page 114 and 115:
Chapter 4 99NNH37CO2EtOH(±)-27a(+)
Page 116 and 117:
Chapter 4 101As already outlined ab
Page 118 and 119:
Chapter 4 103(+)-(S)-2-octylimidazo
Page 120 and 121:
Chapter 4 105CNNH N2 NCN nC 6 H 13N
Page 122 and 123:
Chapter 4 107key step is the conver
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Chapter 4 109reverse addition in th
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Chapter 4 111which was eliminated e
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Chapter 4 113separate (±)-57a and
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Chapter 5 115to avoid this side rea
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Chapter 5 117Complete degradation o
Page 134 and 135:
Chapter 5 119Entry R T °C Product
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Chapter 5 1212:1:3 in weight. All t
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Chapter 5 123reaction conditions we
Page 140 and 141:
Chapter 5 125Entry Substrate R Time
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Chapter 5 127experiments. But it wa
Page 144 and 145:
Chapter 5 129OClOSAM IIPH=7; R.T.OH
Page 146 and 147:
Chapter 5 131OHOXHOHRHK 2 CO 3 ; Me
Page 148 and 149:
Chapter 6 133HCuSO 4 .5H 2 O,NH 4 O
Page 150 and 151:
Chapter 6 1356.2.1 Heteroannullatio
Page 152 and 153:
Chapter 6 137This discovery allowed
Page 154 and 155:
Chapter 6 139OH(±)-62OHFigure 6.1
Page 156 and 157:
Chapter 6 141Entry Substrate R Time
Page 158 and 159:
Chapter 6 143HOH58-a-c,e,h-lRPdCl 2
Page 160 and 161:
Chapter 6 145afforded the benzo[b]f
Page 162 and 163:
Chapter 6 147RR[P(Ph) 3 ]Pd°OHOPh
Page 164 and 165:
Chapter 6 149H2-IodophenolOHOH(±)-
Page 166 and 167:
Chapter 6 151presence of base as de
Page 168 and 169:
Chapter 7 153A chiral lithium alumi
Page 170 and 171:
Chapter 7 155derivatives were tried
Page 172 and 173:
Chapter 7 157Finally an hypothesis
Page 174 and 175:
Chapter 8 159were washed with a sat
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Chapter 8 16145 min, the mixture wa
Page 178 and 179:
Chapter 8 1638.9 Decarboxylation of
Page 180 and 181:
Chapter 8 165Alcohol 27a (0.2 mmol)
Page 182 and 183:
Chapter 8 167for 48 h. After coolin
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Chapter 8 169room temperature for t
Page 186 and 187:
Chapter 8 171in CH 2 Cl 2 and washe
Page 188 and 189:
Chapter 8 1738.26 Screening of lipa
Page 190 and 191:
Chapter 8 175Na 2 SO 4 . After remo
Page 192 and 193:
Chapter 8 177NMR and MS analysis we
Page 194 and 195:
Chapter 8 179Argon was bubbled thru
Page 196 and 197:
Chapter 8 181IR (CHCl 3 ): ν cm-1=
Page 198 and 199:
Chapter 8 183GC-MS: 305 M + (68%),
Page 200 and 201:
Chapter 8 185[α] 20 D -5.7 (c 1.75
Page 202 and 203:
Chapter 8 187Synthetic method 7.7.1
Page 204 and 205:
Chapter 8 189(R,S)-(±)-1-(2-Octyl)
Page 206 and 207:
Chapter 8 191M.P. = oil.Elementary
Page 208 and 209:
Chapter 8 193Synthetic method 7.11.
Page 210 and 211:
Chapter 8 195(±)-N-1-(2-Octyl)-2-t
Page 212 and 213:
Chapter 8 197IR (CHCl 3 ) ν cm-1 =
Page 214 and 215:
Chapter 8 199(±)-1-(4-Fluorophenyl
Page 216 and 217:
Chapter 8 201Physical and spectral
Page 218 and 219:
Chapter 8 203(±)-1-(Phenyl)-2-prop
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Chapter 8 205128.61, 128.87, 130.39
Page 222 and 223:
Chapter 8 207min.Physical and spect
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Chapter 8 20913C J MOD NMR (CDCl 3
Page 226 and 227:
Chapter 8 211(±)-2'-Methylphenyl-2
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Chapter 9 213References chapter 1:1
Page 230 and 231:
Chapter 9 21531) De Felice, R.; Joh
Page 232 and 233:
Chapter 9 21768) Brodie, A.M.H. in
Page 234 and 235:
Chapter 9 219112) Brodie, A. M. H.;
Page 236 and 237:
Chapter 9 2214) Karabatsos, M.C. J.
Page 238 and 239:
Chapter 9 22334c) Blow D. Nature 19
Page 240 and 241:
Chapter 9 22567a) Kundu, N.G.; Pal,
Page 242:
Chapter 9 22712) Thompson,A.S.; Hum
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