By Thilo J. Heckrodt, Johann Mulzer (auth.), Johann Mulzer (eds.)
ISBN-10: 3540211241
ISBN-13: 9783540211242
ISBN-10: 354021125X
ISBN-13: 9783540211259
T.J. Heckrodt and J.H. Mulzer: Marine typical items from Pseudopterogorgia Elisabethae: buildings, Biosynthesis, Pharmacology and overall Synthesis .-
M. Kalesse: Vinylogous Aldol Reactions and their purposes within the Syntheses of normal items .-
U. Beifuss and M. Tietze: Methanophenazine and different traditional Biologically energetic Phenazines .-
H.-J. Knoelker: incidence, organic task, and Convergent Organometallic Synthesis of Carbazole Alkaloids .-
U. Nubbemeyer: cost sped up Aza-Claisen Rearrangements .-
P. Metz: man made experiences at the Pamamycin Macrodiolides
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Extra info for Natural Products Synthesis II: Targets, Methods, Concepts
Sample text
75 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abstract The synthesis of complex natural products still remains as the bottleneck for the biological evaluation of such compounds. In contrast to the biosyntheses, vinylogous aldol reactions can incorporate more than one acetate or propionate building block into the growing polyketide chain. To facilitate such reactions either enolate activation or aldehyde activation is required.
In particular, aliphatic aldehydes give poor yields and selectivities. Protocols for the enantioselective variation are given using either the Tol-BINAP system or C2-symmetrical copper(II) complexes. Keywords Vinylogous · Aldol reaction · Lewis acid · Callipeltoside 44 M. Kalesse Abbreviations and Symbols Ac Acetyl 18-c-6 18-Crown-6 BINAP 2,2¢-Bis(diphenylphosphino)-1,1¢-binaphthyl BINOL Binaphthol Bn Benzyl Bu Butyl Cy cyclohexyl DAST Diethylaminosulfur trifluoride DDQ 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone DET Diethyl tartrate DIBAl-H Diisobutylaluminum hydride DMPU 1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H) pyrimidinone ee Enantiomeric excess Et Ethyl LDA Lithium diisopropyl amide L-selectride Lithium tri-sec-butylborohydride m-CPBA m-Chloroperoxybenzoic acid Me Methyl MOM Methoxymethyl ms Molecular sieves Ms Methanesulfonyl (mesyl) NMO 4-Methylmorpholine N-oxide Ph Phenyl PMB 4-Methoxyphenyl Pr Propyl PPTS Pyridinium p-toluenesulfonate PyBOP Benzotriazol-1-yloxytris(pyrrolidino)phosphonium hexafluorophosphate rt Room temperature TBAF Tetrabutylammonium fluoride TBS tert-Butyldimethylsilyl TBAT Tetrabutylammonium triphenyldifluorosilicate TBDPS tert-Butyldiphenylsilyl TBHP tert-Butyl hydroperoxide TES Triethylsilyl Tf Trifluoromethanesulfonyl (triflyl) TFA Trifluoroacetic acid THF Tetrahydrofuran TMS Trimethylsilyl Tol Toluyl TPAP Tetra-n-propylammonium perruthenate (VII) 1 Introduction Aldol reactions are among the most prominent and most frequently applied transformations, since they build up polyketide fragments of important biologically active compounds such as antibiotics and antitumor compounds.
Heckrodt · J. Mulzer Marine Natural Products from Pseudopterogorgia elisabethae 25 (resulting in the wrong C3 configuration), TBS protection of the primary and MOM protection of the secondary alcohol led to 69, which was then converted into 70 by stereocontrolled hydroboration/oxidation, pivaloyl protection, and desilylation. The stereogenic center at C7 was generated in the undesired configuration, but this was rectified later by epimerization under the Dieckmann cyclization conditions. Compound 70 was transformed into ketolactone 71 by a succession of routine operations.
Natural Products Synthesis II: Targets, Methods, Concepts by Thilo J. Heckrodt, Johann Mulzer (auth.), Johann Mulzer (eds.)
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