The Enantiocontrolled Synthesis of a Highly Functionalized Cyclohexenone Related to the A-Ring of the Furanosteroid Viridin

2009 ◽  
Vol 62 (9) ◽  
pp. 1173 ◽  
Author(s):  
Alison D. Findlay ◽  
Antje Gebert ◽  
Ian A. Cade ◽  
Martin G. Banwell
Keyword(s):  
Starting Material ◽  
Reaction Sequence ◽  
Enantiomerically Pure ◽  
Natural Enantiomer ◽  
Equivalent Sequence

A seven-step reaction sequence has been used to convert the enantiomerically pure cis-1,2-dihydrocatechol 10 into the cyclohexenone 17a. A near equivalent sequence involving the same starting material has allowed for the synthesis of the regioisomeric system 17b. Compound 17a is related to the A-ring of ent-viridin (ent-1), the non-natural enantiomer of the furanosteroid viridin (1).

Synthesis of the four possible stereoisomeric 5′-nor carbocyclic nucleosides from one common enantiomerically pure starting material

1994 ◽  
Vol 35 (13) ◽  
pp. 1961-1964 ◽  
Author(s):  
Natalja Dyatkina ◽  
Burkhard Costisella ◽  
Fritz Theil ◽  
Martin von Janta-Lipinski
Keyword(s):  
Starting Material ◽  
Carbocyclic Nucleosides ◽  
Enantiomerically Pure

Unexpected Formation of Thiophene-annulated Tetrahydro-3- benzazepines by Alkylation of Thiolactams with Ethyl Bromoacetate

2013 ◽  
Vol 68 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Soumya Sarkar ◽  
Roland Fröhlich ◽  
Bernhard Wünsch
Keyword(s):  
Ethyl Bromoacetate ◽  
Reaction Sequence ◽  
Unexpected Formation ◽  
Enantiomerically Pure ◽  
Lawesson’S Reagent ◽  
Sulfide Contraction ◽  
Lawesson's Reagent

In order to synthesize enantiomerically pure tetrahydro-3-benzazepines with diverse substitution patterns, the lactams 3 were converted into thiolactams 4 upon treatment with Lawesson’s reagent. Instead of an Eschenmoser sulfide contraction a thiophene annulation reaction occurred, when the thiolactams 4 were reacted with ethyl bromoacetate. Altogether, enantiomerically pure thiopheneannulated 3-benzazepines 7 were prepared in a very short reaction sequence (five reaction steps) starting from commercially available o-phenylenediacetic acid

scholarly journals Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B

2011 ◽  
Vol 7 ◽  
pp. 421-425 ◽  
Author(s):  
Silke Dubberke ◽  
Muhammad Abbas ◽  
Bernhard Westermann
Keyword(s):  
Total Synthesis ◽  
Building Block ◽  
Building Blocks ◽  
Allylic Rearrangement ◽  
Reaction Sequence ◽  
Enantiomerically Pure ◽  
Quaternary Stereocenter

Enantiomerically highly enriched unsaturated β-ketoesters bearing a quaternary stereocenter can be utilized as building blocks for the synthesis of natural occurring terpenes, i. a., trisporic acid and its derivatives. An advanced building block has been synthesized in a short reaction sequence, which involves an oxidative allylic rearrangement initiated by pyridinium dichromate (PDC) as the key step.

A First Generation Chemoenzymatic Synthesis of (+)-Galanthamine

2010 ◽  
Vol 63 (10) ◽  
pp. 1437 ◽  
Author(s):  
Martin G. Banwell ◽  
Xinghua Ma ◽  
Ochitha P. Karunaratne ◽  
Anthony C. Willis
Keyword(s):  
Total Synthesis ◽  
First Generation ◽  
Claisen Rearrangement ◽  
Starting Material ◽  
Chemoenzymatic Synthesis ◽  
Quaternary Carbon ◽  
Enantiomerically Pure ◽  
Rearrangement Reaction

A total synthesis of (+)-galanthamine [(+)-1] has been achieved using the readily available and enantiomerically pure metabolite 2 as starting material. The quaternary carbon centre (C8a) associated with target 1 was constructed using the Eschenmoser–Claisen rearrangement reaction.

A Practical Synthesis of the Flavone, Scutellarein

2017 ◽  
Vol 41 (3) ◽  
pp. 157-159 ◽  
Author(s):  
Qian Wang ◽  
Xia-li Liao ◽  
Cheng Xiang ◽  
Jian Yang
Keyword(s):  
Scale Up ◽  
Starting Material ◽  
Reaction Sequence ◽  
Practical Synthesis

A practical and economical five-step synthesis of the flavone scutellarein has been achieved in 60% overall yield using the available and cheap 2,6-dimethoxy-1,4-benzoquinone as starting material. The reaction sequence involved reduction to the corresponding quinol, Friedel-Crafts acetylation, Claisen-Schmidt condensation with p-methoxybenzaldehyde, cyclisation and demethylation. The procedure is operationally simple and amenable to scale-up synthesis.

scholarly journals Formal Synthesis of (+)-Madindoline A a Potent IL-6 Inhibitor Utilizing Enzymatic Discrimination of Quaternary Carbon

2013 ◽  
Vol 8 (7) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
Ken-ichi Shimizu ◽  
Mina Tomita ◽  
Ken-ichi Fuhshuku ◽  
Takeshi Sugai ◽  
Mitsuru Shoji
Keyword(s):  
Pure Form ◽  
Starting Material ◽  
Side Chains ◽  
Quaternary Carbon ◽  
Formal Synthesis ◽  
Enantiomerically Pure ◽  
Alkyl Side Chains ◽  
Enzymatic Procedure

A formal synthesis of (+)-madindoline A was achieved. The Sunazuka's key intermediate (4 R,5 S)-(–)-3-butyl-4-( tert-butyldimethylsiloxy)-5-methoxycarbonyl-2,5-dimethyl-2-cyclopentenone was synthesized from easily available (2 S,3 S)-3-acetoxy-2-ethenyl-2-methylcyclopentanone. The starting material was reliably supplied by a chemo-enzymatic procedure in enantiomerically pure form. The synthesis was performed by straightforward transformations involving enone formation and regioselective introduction of the two alkyl side chains.

Crambe abyssinica meal as starting material for the production of enantiomerically pure fine chemicals

1998 ◽  
Vol 7 (2-3) ◽  
pp. 187-193 ◽  
Author(s):  
P Daubos ◽  
V Grumel ◽  
R Iori ◽  
O Leoni ◽  
S Palmieri ◽  
...  
Keyword(s):  
Starting Material ◽  
Fine Chemicals ◽  
Crambe Abyssinica ◽  
Enantiomerically Pure

The Snyder Synthesis of Psylloborine A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Lewis Acid ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Oxidative Cleavage ◽  
Lower Half ◽  
Starting Material ◽  
Enantiomerically Pure ◽  
Free Amine ◽  
Proper Order ◽  
Phenyl Sulfone

In addition to the monomeric coccinellid alkaloids produced by the ladybug, some dimeric alkaloids, exemplified by psylloborine A 3, have been isolated. Scott A. Snyder of Scripps/Florida initially attempted a direct dimerization strategy for the assembly of 3, but when that failed, he devised (J. Am. Chem. Soc. 2014, 136, 9743) a route to the tethered dimer 1, that could indeed be cyclized to 2, the immediate precursor to 3. The starting material for both 9, the lower half of 1, and 13, the upper half of 1, was the commercial, enantiomerically-pure piperidine 4. Metalation followed by allylation gave the desired trans diastereomer 5. Oxidative cleavage followed by con­densation with 6 gave the ester 7, that was hydrogenated, then converted with 8 to the desired phosphonate 9. To prepare 13, 4 was metalated and alkylated with methallyl bromide. The prod­uct 10 was carried on to the enone 12 by oxidative cleavage followed by the addition of 11, oxidative cleavage, and dehydration. Reduction to the desired diastereomer was achieved by conjugate addition of hydride in the presence of the sterically very demanding Yamamoto Lewis acid ATPH. Deprotection followed by oxidation then gave 13, that was condensed with 9 and deprotected to give 14. Selective deprotection followed by oxidation and condensation with 15 then led to 1. A key element in the design of this synthesis was the ability to easily tune the sul­fone activating group, to direct the proper order of bond formation. The vision was that regeneration of the enone and deprotection, with tetramethylguanidine, would lead to 16. The free amine would add to the saturated ketone to give an enamine, that would in turn add in a conjugate sense to the enone to give 17. Further deprotec­tion of 17 under acid conditions would again generate an enamine that, it was hoped, would, after further cyclization, add to the unsaturated sulfone to give 2. As illustrated, the 3,5-bis(trifluoromethyl)phenyl sulfone gave the best results. Desulfurization of 2 completed the synthesis of the complex dimeric alkaloid psylloborine A 3.

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