Improved synthetic route to enantiomerically pure samples of the tetrahydropyran-2-ylacetic acid core associated with the phytotoxic polyketide herboxidiene

2000 ◽  
Vol 53 (8) ◽  
pp. 659 ◽  
Author(s):  
Martin G. Banwell ◽  
Malcolm D. McLeod ◽  
Rajaratnam Premraj ◽  
Gregory W. Simpson

The phosphine oxide (2), which embodies the tetrahydropyran-2-ylacetic acid core associated with the phytotoxic polyketide herboxidiene (1) and which is a key intermediate in a projected synthesis of this natural product, has been prepared in a highly enantio- and diastereo-selective manner. The pivotal steps in this new and improved synthesis of compound (2) involve Katsuki–Sharpless asymmetric epoxidation of the allylic alcohol (4) to give epoxide (7) and subsequent ring-cleavage of the latter compound with trimethylaluminium to give diol (9). The derived acetate (10) is then readily ozonolysed to give the previously reported aldehyde (11), although now in high enantiomeric excess. Compound (11) can be elaborated, by established chemistry, to the target oxide (2).

Synthesis ◽  
2018 ◽  
Vol 50 (24) ◽  
pp. 4796-4808 ◽  
Author(s):  
Leslie Aldrich ◽  
Qiwen Gao ◽  
Lianyan Xu ◽  
Vincent Parise ◽  
Yash Mehta

A concise method that is easily amenable for analogue synthesis has been developed to enantioselectively access 4-amino-3-hydroxybenzopyrans from chalcones. Epoxy alcohols were formed from chalcones through a Corey–Bakshi–Shibata reduction of the enone and subsequent Sharpless asymmetric epoxidation of the allylic alcohol. The epoxy alcohols were protected, regioselectively opened with various amines using catalytic europium(III) triflate, and the resulting free alcohols were orthogonally protected. Concomitant deprotection and intramolecular nucleophilic aromatic substitution provided the benzopyran core, which is poised to undergo additional reactions to provide a diverse chemical library with ideal properties for biological evaluation.


2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Sergio Rossi ◽  
Maurizio Benaglia ◽  
Roberto Cirilli ◽  
Tiziana Benincori

Abstract Novel enantiomerically pure tetramethylbithiophene diphosphine oxides (tetraMe-BITIOPO) featuring differently substituted aromatic rings at the phosphorous atoms were synthesized, fully characterized and isolated in enantiomerically pure form. The new Lewis bases were tested as organocatalysts in two different reactions involving trichlorosilyl compounds. The introduction of electron donating substituents on the aromatic rings connected to the phosphine oxide groups positively affected the chemical and stereochemical catalytic efficiency of these ligands. The new catalysts were able to promote the allylation of aldehydes with allyltrichlorosilane in up to 76% yield and up to 86% enantiomeric excess (ee), and the direct aldol reaction to afford β-hydroxy ketones in high diastereoselectivity (up to 88:12 anti:syn ratio) and up to 72% ee.


2013 ◽  
Vol 66 (9) ◽  
pp. 1105 ◽  
Author(s):  
Timothy M. Altamore ◽  
Oanh T. K. Nguyen ◽  
Quentin I. Churches ◽  
Kate Cavanagh ◽  
Xuan T. T. Nguyen ◽  
...  

A concise synthesis of both E-isomers of 2S-amino-3-(2′-aminomethyl-cyclopropyl)propionic acid, new methano-l-lysines, is described. The synthetic route includes nine steps from l-methionine, with a key step involving the cyclopropanation of an intermediate E-allylic alcohol. The resultant hydroxymethylcyclopropanes were readily separated and converted into the title α-amino acids. The stereochemistry around the cyclopropane rings was deduced by conducting the cyclopropanation in the presence of N,N,N′,N′-tetramethyl-d-tartaric acid diamide butylboronate, a chiral controller which is known to favour the production of S-hydroxymethyl cyclopropanes from allylic alcohols.


Author(s):  
Douglass F. Taber

(-)-Nakiterpiosin 3, isolated from the thin encrusting sponge Terpios hoshinota, has an IC50 against murine P388 leukemia cells of 10 ng/mL. Chuo Chen of UT Southwestern Medical Center developed (J. Am. Chem. Soc. 2010, 132, 371) a practical synthetic route to 3 based on the convergent coupling of 1 and 2. The preparation of 1 was based on the intramolecular [4 + 2] cyclization of the furan 9, prepared by Friedel-Crafts acylation of furan 4 with maleic anhydride 5 . The absolute confi guration of the secondary alcohol was set by Noyori reduction, using sodium formate as the hydride source. The cyclization of 9 to 10 proceeded with high diastereocontrol, presumably by way of a chelated transition state. As expected, cyclization of the silyl ether of 9 delivered the complementary diastereomer. Because the cyclization of 9 was readily reversible, it was taken quickly to the bromide 11. Oxidative cleavage of the diol followed by selective reduction and protection then completed the synthesis of 1. The preparation of 2 began with the commercial bromo acid 12. The enantiomerically enriched epoxide 13 was constructed in the usual way by homologation of the aldehyde to the allylic alcohol followed by Sharpless epoxidation. On exposure to the Yamamoto catalyst, 13 smoothly rearranged to the aldehyde 14. Condensation of 14 with 15 then gave 16, with only minimal erosion of enantiomeric excess over the two steps. Unfortunately, 16 was the incorrect diastereomer, so it had to be inverted. With the aldehyde 17 in hand, conversion to the dichloride followed by functional group interchange completed the construction of 2 . Carbonylative coupling of 1 and 2 led to the enone 18. The photochemical Nazarov cyclization of 18 proceeded with the expected high diastereocontrol, to give, after epimerization, the desired trans-anti-trans product. Deprotection then completed the synthesis of (-)-nakiterpiosin 3. It is noteworthy that the full A-ring functionality of 3 was compatible with the conditions of the photochemical cyclization. The work of Chen toward the total synthesis of (-)-nakiterpiosin 3 led to a correction of the relative configurations both of the dichloromethyl substituent and of the secondary bromide.


ChemInform ◽  
2010 ◽  
Vol 28 (1) ◽  
pp. no-no
Author(s):  
J. KULA ◽  
M. SIKORA ◽  
H. SADOWSKA ◽  
J. PIWOWARSKI

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