scholarly journals Concise Diastereoselective Total Synthesis of (±)-Parvistemonine A

Synlett ◽  
2020 ◽  
Vol 31 (18) ◽  
pp. 1800-1804
Author(s):  
Kazuyuki Sugita ◽  
Rintaro Matsuo ◽  
Ayumu Miyashita ◽  
Motoi Kuwabara ◽  
Shinya Adachi ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Michael Addition ◽  
Wittig Reaction ◽  
Crystallographic Analysis ◽  
Mitsunobu Reaction ◽  
X Ray ◽  
Linear Sequence ◽  
Relative Stereochemistry ◽  
Key Steps ◽  
First Time

AbstractWe have developed a concise diastereoselective total synthesis of (±)-parvistemonine A. By using a Mukaiyama–Michael addition, an aza-Wittig reaction, a Paal–Knorr pyrrole synthesis, an acid-mediated annulation, and a Mitsunobu reaction as key steps, we achieved a total synthesis in which the longest linear sequence was ten steps and the overall yield was 19.6%. Additionally, the relative stereochemistry of parvistemonine A was confirmed by X-ray crystallographic analysis for the first time.

An Approach to the Total Synthesis of Diterpenoid Plant Growth Substances Isolated From Gametophytes of the Fern Genus Anemia

1992 ◽  
Vol 45 (1) ◽  
pp. 227 ◽  
Author(s):  
CKF Chiu ◽  
LN Mander ◽  
AD Stuart ◽  
AC Willis
Keyword(s):  
Total Synthesis ◽  
Liquid Ammonia ◽  
Crystallographic Analysis ◽  
Aldol Reactions ◽  
Growth Substances ◽  
Enol Ether ◽  
X Ray ◽  
Relative Stereochemistry ◽  
Plant Growth Substances

Reduction of the oxoindan acid (9) by potassium in liquid ammonia followed by in situ alkylation with 3-methylbut-2-enyl bromide furnished enol ether (14) which was transformed into the acetal (17) and thence aldehydes (18; R = COCH3 and COCHCl2). Acid- catalysed aldol reactions then afforded the ethanoindene derivatives (19; R=COCH3 and COCHCl2). Further elaboration gave carbinol (28) which is envisaged as an intermediate for the total synthesis of the diterpenoid antheridiogens obtained from gametophytes of the fern genus Anemia, including acid (2). The relative stereochemistry of acetal (17) was established by X-ray crystallographic analysis.

A Chemoenzymatic Total Synthesis of the Undecenolide ( - )-Cladospolide C

2005 ◽  
Vol 58 (7) ◽  
pp. 511 ◽  
Author(s):  
Martin G. Banwell ◽  
David T. J. Loong ◽  
Anthony C. Willis
Keyword(s):  
Total Synthesis ◽  
Single Crystal ◽  
Natural Product ◽  
Absolute Configuration ◽  
Starting Material ◽  
Unsaturated Ester ◽  
Ring Closing Metathesis ◽  
X Ray ◽  
Key Steps ◽  
First Time

The (−)-enantiomer, ent-3, of the natural product (+)-cladospolide C (3) has been prepared for the first time using the monochiral cis-1,2-dihydrocatechol 5 as starting material. Key steps include coupling of the derived acid 6 with the enzymatically generated (S)-(+)-4-penten-2-ol (7) and ring-closing metathesis (RCM) of the resultant doubly unsaturated ester 8 to give lactone 9. The structure of this last compound has been confirmed by single-crystal X-ray analysis. This work has established that the absolute configuration of (+)-cladospolide C has been correctly assigned and is as illustrated in structure 3.

scholarly journals A Brønsted base-promoted diastereoselective dimerization of azlactones

2017 ◽  
Vol 13 ◽  
pp. 2663-2670 ◽  
Author(s):  
Danielle L J Pinheiro ◽  
Gabriel M F Batista ◽  
Pedro P de Castro ◽  
Leonã S Flores ◽  
Gustavo F S Andrade ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Crystallographic Analysis ◽  
Base System ◽  
Reaction Monitoring ◽  
Kinetic Reaction ◽  
X Ray ◽  
H Nmr ◽  
Relative Stereochemistry ◽  
Brønsted Base ◽  
Reaction Profile

A novel Brønsted base system for the diastereoselective dimerization of azlactones using trichloroacetate salts and acetonitrile has been developed. Desired products were obtained in good yields (60–93%) and with up to >19:1 dr after one hour of reaction. Additionally, the relative stereochemistry of the major dimer was assigned as being trans, by X-ray crystallographic analysis. The kinetic reaction profile was determined by using 1H NMR reaction monitoring and revealed a second order overall kinetic profile. Furthermore, by employing this methodology, a diastereoselective total synthesis of a functionalized analogue of streptopyrrolidine was accomplished in 65% overall yield.

The Total Synthesis of Rhabdastrellic Acid A

2018 ◽  
Author(s):  
Yaroslav Boyko ◽  
Christopher Huck ◽  
David Sarlah
Keyword(s):  
Total Synthesis ◽  
Late Stage ◽  
Cross Coupling ◽  
Side Chains ◽  
General Strategy ◽  
Modular Approach ◽  
Linear Sequence ◽  
Generating Sequence ◽  
First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained <i>trans-syn-trans</i>-perhydrobenz[<i>e</i>]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a <i>p</i>-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

Isolation and structure of combretastatin

1982 ◽  
Vol 60 (11) ◽  
pp. 1374-1376 ◽  
Author(s):  
George R. Pettit ◽  
Gordon M. Cragg ◽  
Delbert L. Herald ◽  
Jean M. Schmidt ◽  
Prasert Lohavanijaya
Keyword(s):  
Total Synthesis ◽  
South African ◽  
Spectral Methods ◽  
Biological Evaluation ◽  
Crystallographic Analysis ◽  
Structural Elucidation ◽  
The South ◽  
X Ray

The South African tree Combretumcaffrum has been shown to contain a constituent capable of significantly reversing astrocyte formation employing the National Cancer Institute's 9ASK system. The constituent responsible for astrocyte reversal was isolated and designated combretastatin (1). Structural elucidation was initiated employing spectral methods and completed by X-ray crystallographic analysis. By this means combretastatin was assigned structure 1. Further biological evaluation and a total synthesis are now in progress.

scholarly journals Addition of some 6-amino-4-aryl-2(1H)-pyridones to phenylisocyanate and related reactions

2019 ◽  
Vol 74 (2) ◽  
pp. 191-195
Author(s):  
Lyubomir Dimitrov Raev ◽  
Ivo Christov Ivanov ◽  
Silviya Georgieva Agontseva
Keyword(s):  
Michael Addition ◽  
Acetyl Derivative ◽  
Phenyl Isocyanate ◽  
Crystallographic Analysis ◽  
Molar Ratio ◽  
X Ray ◽  
The Michael Addition

AbstractThe Michael addition of enaminoesters to coumarins leads to the formation of the rearranged adduct 1 whose structure has been previously elucidated by X-ray crystallographic analysis. Now, N- and/or O-carbamoylation of the 6-amino-2-pyridone 1 by treatment with phenyl isocyanate in a molar ratio of 1:1 and 1:2 gave N-mono- (2a) or N,O-bis-(phenylcarbamoyl) (3) derivatives, respectively. Further transformations of the corresponding new 2-pyridone derivative 2a into the O-acetyl derivative 2b and the chromeno[3,4-c]pyridine 4 are reported as well.

The Crystal Structure of Dimethyl (1aα,2aα,5β,6aβ-Hexahydroazirino[2,1-b]benzoxazole-1a, 5(1H)-dicarboxylate

1991 ◽  
Vol 44 (8) ◽  
pp. 1145 ◽  
Author(s):  
MF Mackay ◽  
M Campbell ◽  
MJ Mcleish
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Crystallographic Analysis ◽  
Aminobenzoic Acid ◽  
X Ray ◽  
Relative Stereochemistry

The title compound formed the major component in a rearrangement of an analogue of 4-amino-4-deoxychorismic acid (1), an intermediate in the chorismate-p-aminobenzoic acid biotransformation. X-Ray crystallographic analysis has defined the relative stereochemistry at the four chiral centres in the tricyclic molecule.

Studies Directed Towards the Total Synthesis of Anticapsin. X-Ray Crystal-Structure of (1RS,2SR,4RS,5RS,6SR)-5-Hydroxy-2-phthalimido-1-trimethylsilyloxy-bicyclo[2.2.2]octane-2,6-carbolactone

1990 ◽  
Vol 43 (11) ◽  
pp. 1827 ◽  
Author(s):  
MJ Crossley ◽  
TW Hambley ◽  
AW Stamford
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Total Synthesis ◽  
Synthetic Approach ◽  
Hydrogen Atoms ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Relative Stereochemistry ◽  
Atomic Parameters

The relative stereochemistry of methyl 2-phthalimido-1- trimethylsilyloxybicyclo[2.2.2]oct-5-ene-2-carboxylate (9) and its 5,6-epoxide (10), intermediates in a synthetic approach to the amino acid antibiotic anticapsin, were established by the TiCl4-mediated cyclization of (10) to the carbolactone (12); the structure of which was proved by single-crystal X-ray crystallography. Full-matrix least- squares refinement of all atomic parameters with individual isotropic thermal parameters for the hydrogen atoms by using 1446 reflections converged at R 0.036. Crystals of (12) are monoclinic, P21/c, a 12.342(3), b 12.239(2), c 13.405(3) Ǻ, β 99.34(2)°, Z 4.

A Base-Promoted One-Pot Asymmetric Friedel–Crafts Alkylation/Michael Addition of 4-Substituted Indoles

Synthesis ◽  
2019 ◽  
Vol 52 (08) ◽  
pp. 1215-1222
Author(s):  
Robert Connon ◽  
Laura Carroll ◽  
Patrick J. Guiry
Keyword(s):  
Michael Addition ◽  
Crystallographic Analysis ◽  
Indole Derivatives ◽  
One Pot ◽  
X Ray ◽  
Excellent Yield ◽  
Tricyclic Core ◽  
Cyclobutane Derivative

Herein, we report a base-promoted Zn(II)–bis(oxazoline)-catalyzed one-pot Friedel–Crafts alkylation/Michael addition of 3-(indol-4-yl)acrylonitrile derivatives with trans-β-nitrostyrenes to yield the tricyclic core of the ergoline skeleton in up to 71% yield and 85% ee. During the purification of 3-(indol-4-yl)acrylonitrile, the key substrate for catalytic studies, a novel trans-cis-trans-cyclobutane derivative, thought to be formed via a [2+2] light-promoted cycloaddition, was identified by X-ray crystallographic analysis. Finally, a novel class of 4-substituted bis(indole)methane derivatives were serendipitously prepared in excellent yield by reacting 4-substituted indole derivatives with 4-nitrobenzaldehyde. One bis(indole)methane was characterized by X-ray crystallographic analysis.

Base mediated dimerization of 2-tetradecynoic acid

1983 ◽  
Vol 61 (11) ◽  
pp. 2449-2454 ◽  
Author(s):  
Suzanne R. Abrams ◽  
J. Wilson Quail ◽  
Louis T. J. Delbaere
Keyword(s):  
Sodium Salt ◽  
Michael Addition ◽  
Dimethyl Ester ◽  
Crystallographic Analysis ◽  
Strong Base ◽  
X Ray ◽  
Crude Product ◽  
Monomethyl Ester

Under the influence of the very strong base, the sodium salt of 1,2-diaminoethane in 1,2-diaminoethane, 2-tetradecynoic acid is converted to 3-tetradecynoic acid (35%) and a novel dimer 3. Compound 3 ((Z)-2-(1-dodecynyl)-3-undecyl-pent-2-en-1,5-dioic diacid) is isolated as the monomethyl ester 1 after treatment of the crude product with methanolic HCl. The structures of 1 and 3 are deduced from an X-ray crystallographic analysis of the dimethyl ester 2 obtained by reaction of 1 with diazomethane. The dimer 3 is thought to arise from Michael addition of the dianion 4 of 3-tetradecynoic acid with the sodium salt of 2-tetradecynoic acid.

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