scholarly journals Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C 2-symmetric building block: a strategy for the synthesis of decanolide natural products

2013 ◽  
Vol 9 ◽  
pp. 2544-2555 ◽  
Author(s):  
Bernd Schmidt ◽  
Oliver Kunz
Keyword(s):  
Building Block ◽  
Ring Opening ◽  
Kinetic Resolution ◽  
Membered Ring ◽  
Ring Closure ◽  
Ring Closing Metathesis ◽  
Cross Metathesis ◽  
Key Steps ◽  
A Site ◽  
Site Selective

Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

scholarly journals Enantioselective Synthesis of the Ethyl Analog of the Marine Alkaloid Haliclorensin C

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1069
Author(s):  
Guillaume Guignard ◽  
Núria Llor ◽  
David Pubill ◽  
Joan Bosch ◽  
Mercedes Amat
Keyword(s):  
Building Block ◽  
Amino Alcohol ◽  
Ring Opening ◽  
Enantioselective Synthesis ◽  
Ring Closing Metathesis ◽  
Biological Screening ◽  
Marine Alkaloid ◽  
Key Steps

The enantioselective synthesis (3.7% overall yield in nine steps from 2) and biological screening of the ethyl analog of the macrocyclic marine alkaloid haliclorensin C (compound 5) are reported. Amino alcohol 3, generated by a LiNH2BH3-promoted reductive ring-opening/debenzylation sequence from phenylglycinol-derived lactam 2, was used as the starting chiral linear building block. Incorporation of the undecene chain via the nosyl derivative 12, methylenation of the pentanol moiety, and a ring-closing metathesis are the key steps of the synthesis.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

Synthesis of a C1–C12 Fragment of Gulmirecin B

Synlett ◽  
2019 ◽  
Vol 30 (11) ◽  
pp. 1346-1350 ◽  
Author(s):  
Rathikrishnan Rengarasu ◽  
Martin E. Maier
Keyword(s):  
Malic Acid ◽  
Building Block ◽  
Macrolide Antibiotic ◽  
Enoic Acid ◽  
Vinyl Bromide ◽  
Asymmetric Dihydroxylation ◽  
Cross Metathesis ◽  
Key Steps

The synthesis of a C1–C14 fragment of the macrolide antibiotic gulmirecin B through formation of the C7–C8 bond by addition of a vinyllithium intermediate to a C1–C7 aldehyde was investigated. This crucial coupling was successful with a vinyllithium reagent corresponding to a C8–C12 fragment. The C8–C12 vinyl bromide was prepared from l-malic acid. The C1–C7 aldehyde building block was synthesized from hex-5-enoic acid by using an Evans alkylation, a cross-metathesis, and an asymmetric dihydroxylation as key steps.

A Stereoselective Synthesis of the ACE Inhibitor Trandolapril

Synlett ◽  
2019 ◽  
Vol 30 (07) ◽  
pp. 813-816 ◽  
Author(s):  
Slim Chiha ◽  
Matthias Spilles ◽  
Jörg-Martin Neudörfl ◽  
Hans-Günther Schmalz
Keyword(s):  
Acid Derivative ◽  
Building Block ◽  
Ace Inhibitor ◽  
Stereoselective Synthesis ◽  
Pyroglutamic Acid ◽  
Ring Closing Metathesis ◽  
12 Steps ◽  
Key Steps

A conceptually novel and stereoselective synthesis of the enantiopure octahydroindole building block and its conversion into the ACE inhibitor trandolapril was achieved. Key steps include the α-allylation of a protected l-pyroglutamic acid derivative, a highly diastereoselective Hosomi–Sakurai reaction and a Ru-catalyzed ring-closing metathesis of a 4,5-diallylated proline. This way, the synthesis of trandolapril was efficiently achieved in 25% overall yield (12 steps).

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