Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products

258 Pages·2000·4.86 MB·English

by  Jean-Claude Braekman

79
Fortschritte der Chemie
organischer Na turstoffe
Progress in the
Chemistry of Organic
Natural Products
Founded by
L. Zechmeister
Edited by
W. Herz, H. Falk,
G. W. Kirby, and R. E. Moore
Authors:
J. C. Braekman, D. Daloze, H. Franzyk,
J. M. Pasteels, and S. Leclercq
Springer-V erlag Wien GmbH
Prof. W. HERZ, Department of Chemistry,
The Florida State Vniversity, Tallahassee, Florida, V.S.A.
Prof. H. FALK, Institut fiir Chemie,
Johannes-Kepler-Vniversităt, Linz, Austria
Prof. G. W. KIRBY, Chemistry Department,
The Vniversity of Glasgow, Glasgow, Scotland
Prof. R. E. MOORE, Department of Chemistry,
Vniversity of Hawaii at Manoa, Honolulu, Hawaii, V.S.A.
This work is subject to copyright.
All rights are reserved, whether the whole or part of the material is concemed, specifically
those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by
photocopying machines or similar means, and storage in data banks.
© 2000 by Springer-Verlag Wien
Origina1ly published by Springer-Verlag I Wien in 2000
Softcover reprint ofthe hardcover lst edition 2000
Library of Congress Catalog Card Number AC 39-1015
Typesetting: Thomson Press (India) Ltd., New Delhi
Graphic design: Ecke Bonk
Printed on acid-free and chlorine-free bleached paper
SPIN: 10743105
With 11 Figures
ISSN 0071-7886
ISBN 978-3-7091-7235-3 ISBN978-3-7091-6341-2(eBook)
DOI 10.1007/978-3-7091-6341-2
Contents
ListofContributors ... ........................................ VII
Synthetic AspectsofIridoid Chemistry
ByH.FRANZYK . •.• •. •. •. • . • . .. . . .• .. . . . . . . . •. •. • . •. •. •• ••• ••
I. Introduction............................................... 2
2. Classification of Iridoids...................................... 2
2.1. IridoidGlycosides....................................... 3
2.2. Non-GlycosidicIridoids................................... 6
2.3. Nitrogen-ContainingCompounds............................. 7
3. AvailabilityandProductionof Iridoids ............................ 8
3.1. Plant Sources .......................................... 9
3.2. Cel1-Cultures........................................... 10
3.3. Isolationand PurificationMethods............................ II
4. Semi-Synthetic ConversionsBetween Iridoids....................... 13
4.1. Hydrolysisand Lactonization ............................... 14
4.2. Decarboxylationof IridoidGlucosides......................... 15
4.3. ReductionandOxidation ofIridoidGlucosides................... 17
4.4. Miscel1aneousTransformationsUsed inStructure Elucidation......... 22
4.5. Non-GlucosidicIridoids................................... 25
4.6. Ring-CleavageSequences andSccoiridoid Chemistry .............. 36
5. MonoterpeneAlkaloidsStructural1yRelatedto Iridoids ................ 45
5.1. PMTAs- Natural Compoundsor Artifacts? ..................... 45
5.2. Semi-Synthesisof PyridineMonoterpene Alkaloids................ 48
5.3. Bacterial Metabolismof IridoidGlucosides ..................... 52
5.4. TotalSynthesisof PyridineMonoterpeneAlkaloids................ 55
5.5. DiversityofBicyclicCyclopentanoidPiperidines ................. 59
5.6. Synthesisof BicyclicCyclopentanoid Piperidines ................. 59
5.7. Semi-Synthesisof Glucosidic Secoiridoid Alkaloids ............... 67
6. SynthesesfromIridoids....................................... 69
6.1. FormationofColoredCompounds............................ 69
6.2. ReactionsofSecoiridoids.................................. 73
6.3. Preparation of Marine Diterpenoids........................... 82
6.4. Building BlocksforOtherTypesofCyclopentanoids............... 87
6.5. ModificationsoftheSugarMoiety inIridoidGlucosides ............ 103
References.................................................. 106
VI Contents
The Defensive ChemistryofAnts
ByS.LECLERCQ,J.C.BRAEKMAN, D.DALOZE,andJ.M.PASTEELS 115
I. Introduction 116
2. Alkaloids ... ............................................. 118
2.1. Structures,Occurrence,and Function 118
2.1.1. Piperidinesand Pyridines ............................. 118
2.1.2. Pyrrolidinesand Pyrrolines 120
2.1.3. Pyrrolizidines ..................................... 122
2.1.4. Indolizidines 124
2.1.5. Tetraponerines 126
2.1.6. Other Alkaloids 127
2.2. Synthesis ............................................. 128
2.2.1. Piperidines ....................................... 128
2.2.2. Pyrrolidines 131
A. SynthesisofRacemicPyrrolidines .................... 131
B. Synthesesof NonracemicPyrrolidines .. 139
2.2.3. Pyrrolines 149
2.2.4. Pyrrolizidines ..................................... 152
2.2.4.1. 3,5-Dialkylpyrrolizidines ................. 152
A. Xenovenine 152
B. (5E,8E)-3-Butyl-5-hexylpyrrolizidine ............ 159
2.2.4.2. 3-Methyl-5-alkenylpyrrolizidinesand
3,5-Dialkenylpyrrolizidines 160
2.2.5. Indolizidines 163
2.2.5.1. Monomorine I 163
A. SynthesesofRacemic Monomorine I ............ 163
B. Synthesesof Nonracemic Monomorine I 173
2.2.5.2. 3,5-Dialkylindolizidines ........................ 190
A. 3-Butyl-5(4-penten-l-yl)indolizidine 190
B. 3-Ethyl- and 3-Hexyl-5-methylindolizidines 193
C. Myrrnicarin 237A and 237B .................. 194
D. Myrrnicarin 217 198
2.2.6. Tetraponerines 200
A. SynthesesofRacemic Tetraponerines .................. 200
B. Synthesesof NonracemicTetraponerines 205
3. Nonalkaloidal Compounds 211
4. Biosynthesis .. ............................................ 217
References 221
Author Index ............................................... 231
Subject Index , 239
List of Contributors
Jean-Claude Braekman, Laboratory of Bio-Organic Chemistry, Department of Organic
Chemistry,CP160/07,UniversityofBrussels,Av.F.D.Roosevelt,50,B-1050Brussels,
Belgium
Desire Daloze,Laboratory ofBio-OrganicChemistry,Departmentof Organic Chemistry,
CP 160/07,UniversityofBrussels, Av.F.D.Roosevelt,50,B-1050 Brussels, Belgium
HenrikFranzyk,DepartmentofOrganicChemistry,TheTechnicalUniversityofDenmark,
Building 201, DK-2800Lyngby, Denmark
SabineLeclercq,LaboratoryofBio-OrganicChemistry,DepartmentofOrganicChemistry,
CP 160/07,Universityof Brussels, Av.F.D.·Roosevelt,50,B-1050 Brussels, Belgium
Jacques M.Pasteels, Laboratoryof Animal and CellularBiology,CP 160112,University
of Brussels, Av.F.D.Roosevelt, 50,B-1050 Brussels, Belgium
Synthetic Aspects of Iridoid Chemistry
H. Franzyk
Department ofOrganic Chemistry,TheTechnical University of
Denmark, Lyngby, Denmark
Contents
I. Introduction................................................ 2
2. Classification of Iridoids ....................................... 2
2.1. lridoid Glycosides ........................................ 3
2.2. Non-Glycosidic Iridoids.................................... 6
2.3. Nitrogen-Containing Compounds.............................. 7
3. Availability and Production of Iridoids ............................. 8
3.1. PlantSources ........................................... 9
3.2. Cell-Cultures............................................ 10
3.3. Isolation and Purification Methods............................. II
4. Semi-Synthetic Conversions Between Iridoids ........................ 13
4.1. Hydrolysis and Lactonization ................................ 14
4.2. Decarboxylation ofIridoid Glucosides.......................... 15
4.3. Reduction and Oxidation of Iridoid Glucosides.................. .. 17
4.4. Miscellaneous Transformations Usedin Structure Elucidation.......... 22
4.5. Non-Glucosidic Iridoids.................................... 25
4.6. Ring-Cleavage Sequences and Secoiridoid Chemistry ............... 36
5. Monoterpene Alkaloids Structurally Related to Iridoids.................. 45
5.1. PMTAs- Natural Compounds or Artifacts? ...................... 45
5.2. Semi-Synthesis of Pyridine Monoterpene Alkaloids................. 48
5.3. Bacterial Metabolism of Iridoid Glucosides ...................... 52
5.4. TotalSynthesis of Pyridine Monoterpene Alkaloids................. 55
5.5. Diversityof Bicyclic Cyclopentanoid Piperidines ... ............... 59
5.6. Synthesis of BicyclicCyclopentanoid Piperidines .................. 59
5.7. Semi-Synthesis of Glucosidic Secoiridoid Alkaloids ................ 67
6. Synthesesfrom Iridoids........................................ 69
6.1. Formation ofColored Compounds............................. 69
6.2. Reactions ofSecoiridoids ................................... 73
6.3. Preparation of Marine Diterpenoids............................ 82
J. C. Braekman et al. Progress in the Chemistry of Organic Natural Products
© Springer-Verlag/Wien 2000
2 H.Franzyk
6.4. BuildingBlocksforOtherTypesof Cyclopentanoids................ 87
6.5. Modificationsofthe Sugar Moiety inIridoid Glucosides ............ 103
References.................................................. 106
1. Introduction
The aim of the present review is to cover developments in the
chemistry of iridoids and related compounds during the last decade. In
order to be able to give a broad, but still comprehensive presentation of
this vast area some limitations to the subject were necessary.
Accordingly, the chemotaxonomic importance and biosynthesis studies
of iridoids will be omitted from the present survey since these subjects
have been treated in contemporary reviews (1-4). Similarly, biological
activity (5) and ecological aspects of iridoids (6, 7) will not be treatedin
detail here. A more historical introduction to the chemistry of iridoids
has already been given (8), and in addition a specialized report on the
progressof synthetic iridoid chemistryhas appeared(9).Here, itisrather
intendedtoprovidethe readerwith an overview of the types ofchemical
reactions that have recently been applied to iridoids and to present a
collectionof synthetic possibilities which should give some perspectives
for future work in this field.
First a brief introduction to typical structural features of iridoids is
presented. It should be emphasized that the subdivision employedhere is
strictly structural (10,11) - somewhat different subclasses would be the
result if biosynthetic relationships were applied (1,2).Both direct isola
tion from plants and production by cell-cultures can be used for
obtaining iridoids, which in tum may be regarded either as starting
material for synthesis of other compounds or as synthetic targets
themselves. Regarding the latter possibility, only conversions between
different iridoids will be discussed in depth in the present review.
However, iridoid related monoterpene alkaloids have been included in
the present survey and will receive considerable attention, as will the
synthetic utility of iridoid-derived building blocks.
2. Classification of Iridoids
The group of monoterpenoid compounds recognized as iridoids
comprises at present well above 1200 structures which exhibit a
remarkable diversity that will be outlined briefly. First a fundamental
References,pp. 106-1/4
Synthetic AspectsofIridoid Chemistry 3
distinction between iridoid glycosides and non-glycosidic iridoid
compounds will be made.
Throughout the present review trivial names (typically having
suffixessuch as-inor-oside) will beused since theIUPACnomenclature
often istoo complex and lengthy even for very simple structures, e.g.the
general carbocyclic skeleton (R= Glc in Chart 1)would be named (5)
1-~-D-glucopyranosyl-4,7-dimethyl-l,4a,5,6,7,7a-hexahydro-cyclopenta
[c]pyran. In many cases the iridoid numbering shown (Chart 1) will be
retained, even when another numbering may be equally appropriate, to
facilitate recognition of the iridoid skeleton in strongly modified
congeners.
2.1. Iridoid Glycosides
The iridoid glycosides themselves may be further subdivided into
carbocyclic iridoids and secoiridoids, and their common feature is the
dihydropyran ring system. In general a ~-D-glucopyranosyl unit is
attached at C-l viaa ~-hemiacetalic bond (Chart 1).The non-glycosidic
part of an iridoid glycoside is often referred to as the aglycone or the
"genin".
Carbocyclic Secoiridoid
Chart 1. Basic skeletonsofiridoid glycosides
Most carbocyclic iridoids have a cis-fused cyclopentane ring with
substituents at C-5 and C-9 in ~-positions (i.e. out of the plane of the
paper), but recently a few trans-fused compounds have been reported
(12). Avaststructuraldiversity ofcarbocyclic iridoids arises from simple
modifications of the cyclopentane ring exemplified by some typical
functionalities: hydroxy, acyloxy, keto, epoxy, chloro, and olefin. In
addition theoxidation stateofC-ll mayrange from methyl tocarboxylic
acid (andesters thereof). But also the basic skeleton exhibits variation as
a result of decarboxylation, thus C-IO and/or C-II may be absent.
The secoiridoids have a basic skeleton in which the carbon-carbon
bond between C-7 and C-8 has been cleaved, but secoiridoids always
contain all original ten aglycone carbon atoms. In secoridoids the
oxidation state of C-7 and C-8/C-9/C-l0 may vary, while C-II is at the
4 H.Franzyk
Cs-Iridoids:
tv C,"W
HO OH
OGle HO OGle
Unedoside(1) Thunbergioside(2)
Cg-Iridoidswithninthcarbon ontCQ-4: 0H
Me 9$"'
HHOO "OH~
HO OGle OGle o OGle
Seabrosidol(3) Epoxydeealoside(4) Randioside(5)
Cg-Iridoidswithninthcarbon onC-8:
tv
HM 2.=Q
r-:
HO OGle HO/ OGle - OGle
Aueubin(6) Catalpol(7) Antirrhinoside(8)
HOW"' ¢IS
~~H
OGle - OGle OGle
Loganin(9) Plantarenaloside(10) Gardoside(11)
Bisiridoids:
~ty
HO - OGle HO/' OGle
Radiatoside(12)
Chart 2. Carbocyclic iridoid glycosides (l0,11,13)
References,pp. 106-1/4