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

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Chapter 2 37RsORmRmRsRLRL RRRLH - A A BOH -CRAMRmRsOHHRScheme 2.1: Reduction of ketones: Cram's rule.The results in the reduction of α-halo-ketones or aldehydes wereanomalous and led to Cornforth's dipolar model C (Scheme 2.2), inwhich the dipoles of the carbonyl group and the carbon-halogen bondwere in an antiperiplanar arrangement. Reduction then proceeded fromthe less hindered side of the ketone C leading to alcohol D 2 (Scheme 2.2).RsORLRLRsH - Cl RCl RClC C DOH -CornforthRLRsOHHRScheme 2.2: Reduction of ketones: Cornforth model.The possibility of chelation in case the α-substituent X was anhydroxy, alkoxy or amino group was covered by Cram's cyclic or chelatemodel E 3 (Scheme 2.3). The chelating group X and the carbonyl groupwere eclipsed and coordinated to the metal M. The reduction occurs againfrom the less hindered side. This model has been widely used torationalize the diasteroselectivity in reduction of ketones E whenchelation is important, depending on the nature of the substituent X andthe metal ion M (Scheme 2.3).MXORLXRLRs RRs R Chelate Cram RLH - RsE E FMOH -XHOHRScheme 2.3: Reduction of ketones: Cram's chelate model.Informations regarding the ground state conformation of carbonylcompounds demonstrated that the conformation in which one bond is
Chapter 2 38eclipsing the carbonyl group is energetically favored. This led Karabatsos topropose an alternative model 4 . Calculation suggested that the most favoredconformation G ( Scheme 2.4) would have the medium size group R M ofthe ketone G eclipsing the carbonyl group, and addition of the hydridewould occur from the side of the less bulky substituent R S to give thealcohol H ( Scheme 2.4 ).Rm ORm O H - RmRLRLH - Rs Rs R Karabatsos RLR RsG G HHOHRScheme 2.4: Reduction of ketones: Karabatsos model.A comparison of the other possible transition state with thisconformation allowed the magnitude of diasteroselectivity to be correlatedwith the experimental results.The most influential contribution towards the interpretation of 1,2asymmetric inductions in carbonyl group reductions was that of Felkin 5 .Attention was directed for the first time to the structure of the transitionstate, which was assumed to be very similar to that of the substrate.Torsional strain caused by interactions between the partially formedhydride-carbonyl bond and the full bonds at the adjacent centre wasassumed to cause attack perpendicular to the carbonyl group plane andstaggered to the largest or more electronegative group R L . The angle ofapproach was later revised by the Burgi-Dunitz trajectory 6a-c , derived fromcrystallographic studies. It placed the incoming hydride much closer to thesubstituent R S . This interaction was decisive for the selection of thistransition state over the alternative one, in which the position of the small R Sand the medium R M would be exchanged.Importantly and in agreement with the Felkin model, if two alkylsubstitutions are present, the more stable conformation has the larger groupperpendicular to the carbonyl group and points the remaining alkyl groupaway from the incoming nucleophile.2.1.2.1. Cyclic Carbonyl Compounds.
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 46 and 47: Chapter 1 31Enantioselective synthe
Page 48 and 49: Chapter 1 33+R,S DRUG ANCHOR R MOLE
Page 50 and 51: Chapter 1 35solubilized in hot etha
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
Page 106 and 107:
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
Page 124 and 125:
Chapter 4 109reverse addition in th
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Chapter 4 111which was eliminated e
Page 128 and 129:
Chapter 4 113separate (±)-57a and
Page 130 and 131:
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
Page 136 and 137:
Chapter 5 1212:1:3 in weight. All t
Page 138 and 139:
Chapter 5 123reaction conditions we
Page 140 and 141:
Chapter 5 125Entry Substrate R Time
Page 142 and 143:
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
Page 176 and 177:
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
Page 184 and 185:
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
Page 220 and 221:
Chapter 8 205128.61, 128.87, 130.39
Page 222 and 223:
Chapter 8 207min.Physical and spect
Page 224 and 225:
Chapter 8 20913C J MOD NMR (CDCl 3
Page 226 and 227:
Chapter 8 211(±)-2'-Methylphenyl-2
Page 228 and 229:
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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