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.

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.

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.

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.

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.

(3E)-5-Hydroxy-3-[5-(hydroxymethyl)furan-2-ylmethylene]-1-benzofuran-2(3H)-one

2007 ◽  
Vol 63 (11) ◽  
pp. o4354-o4354
Author(s):  
Hong-Yan Ma ◽  
Ji Shi ◽  
Chang-Hong Wang ◽  
Zheng-Tao Wang
Keyword(s):  
Hydrogen Bonds ◽  
Spectroscopic Data ◽  
Furan Ring ◽  
Crystallographic Analysis ◽  
Relative Configuration ◽  
X Ray ◽  
H Nmr ◽  
Compound C ◽  
A Chain ◽  
C Nmr

The title compound, C14H10O5, was isolated from Senecio cannabifolius Less var. integrifolius aqueous extract. The structure was elucidated on the basis of spectroscopic data, including MS, 1H NMR and 13C NMR, and the relative configuration was confirmed by X-ray crystallographic analysis. The benzofuran ring is almost coplanar with the furan ring [dihedral angle = 10.47 (15)°]. A chain is formed through supramolecular R 2 2(10) synthons and three-centre hydrogen bonds.

scholarly journals Synthesis of Some Biologically Important 3-Oxacepham Derivatives

1970 ◽  
Vol 5 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Mohammad Rafiqul Islam ◽  
Mohammad Nurnabi ◽  
AM Sarwaruddin Chowdhury ◽  
Mohammad Mehdi Masud
Keyword(s):  
Key Words ◽  
Full Text ◽  
Crystallographic Analysis ◽  
High Yield ◽  
Methyl Group ◽  
X Ray ◽  
Tert Butyl ◽  
Relative Stereochemistry

The 6H-oxathiazines 1a-e having imine moiety underwent [2+2] cycloaddition with phenoxyacetylchloride in the presence of Et3N to give β-lactam derivatives 2a-e in high yield. The X-ray crystallographic analysis revealed the relative stereochemistry that the substituents at C-2 and C-4 were cis configurated. The subtituents at C-6 and C-7 were also cis to each other. However, the 6H-oxathiazines 1f-i containing tert-butyl or methyl group at C-4 did not undergo the cycloaddition. Key words: Azetedinone, β-lactam, oxacepham, cycloaddition, imine, ketene, oxathiazine. Dhaka Univ. J. Pharm. Sci. Vol.5(1-2) 2006 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

scholarly journals 2-Deoxy-2-fluoro-2-C-methyl-D-ribono-1,4-lactone (fluoromethylrib)

2006 ◽  
Vol 62 (4) ◽  
pp. o1208-o1210
Author(s):  
Samuel Parker ◽  
David Watkin ◽  
Benjamin Mayes ◽  
Richard Storer ◽  
Sarah Jenkinson ◽  
...  
Keyword(s):  
Title Compound ◽  
Crystallographic Analysis ◽  
Ring Size ◽  
X Ray ◽  
Compound C ◽  
Relative Stereochemistry

The relative stereochemistry of the fluoro substituent (as ribo) and the ring size of the lactone (as five) in the title compound, C6H9FO4, have been established by X-ray crystallographic analysis.

Synthesis and characterization of novel azo-embedded N-confused tetraphenylporphyrin

2009 ◽  
Vol 13 (02) ◽  
pp. 215-222 ◽  
Author(s):  
Motoki Toganoh ◽  
Takayoshi Hihara ◽  
Kentaro Yonekura ◽  
Yuichi Ishikawa ◽  
Hiroyuki Furuta
Keyword(s):  
Absorption Spectrum ◽  
Effective Interaction ◽  
Coupling Reaction ◽  
Crystallographic Analysis ◽  
Synthesis And Characterization ◽  
X Ray ◽  
H Nmr ◽  
Cis Isomer ◽  
C Nmr

A unique class of azo porphyrin, 5,10,15,20-tetraphenyl-21-phenylazo-(2-aza-21-carbaporphyrin 1, in which an azophenyl group is embedded in N -confused porphyrin, was synthesized and characterized by 1 H NMR, 13 C NMR, UV-vis absorption, MS, and X-ray crystallographic analysis. Synthesis of 1 was achieved through a coupling reaction of 21-amino N -confused tetraphenylporphyrin with nitrosobenzene and subsequent deoxygenation of resulting azoxy derivative with a trioxo rhenium(VII) N -fused porphyrinato catalyst. The azo-conjugate molecule was exclusively obtained as a trans-isomer and no isomerization to the cis-isomer was observed under thermal or photoirradiation. The absorption spectrum of 1 shows a moderate red-shift due to the effective interaction between the porphyrinic π-system and the connecting azophenyl group. Upon protonation, this effect is essentially lost as a result of removing degeneracy of LUMO and LUMO+1.

Total Synthesis of (±)-Iso-trans-trikentrin B

1998 ◽  
Vol 51 (3) ◽  
pp. 177 ◽  
Author(s):  
John K. MacLeod ◽  
Annemarie Ward ◽  
Anthony C. Willis
Keyword(s):  
Crystal Structure ◽  
Total Synthesis ◽  
Marine Sponge ◽  
Title Compound ◽  
Compound A ◽  
X Ray ◽  
Relative Stereochemistry ◽  
Synthetic Sequence

The synthesis of the title compound, a member of a family of cyclopent[g]indoles isolated from a marine sponge, is described. Most of the synthetic sequence was developed starting from the more readily available cis-1,3-dimethylindan. An X-ray crystal structure of the indanol (24), the precursor of trans-1,3-dimethylindan, confirmed its relative stereochemistry.

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