Synthesis of new heterocyclics from epoxypulegone (original) (raw)
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Synthetic Study of Natural Metabolites Containing a Benzo[c]oxepine Skeleton: Heterocornol C and D
International Journal of Molecular Sciences
A versatile strategy for the enantioselective synthesis of a benzo[c]oxepine structural core containing natural secondary metabolites was developed. The key steps of the synthetic approach include ring-closing alkene metathesis for seven-member ring construction, the Suzuki–Miyaura cross-coupling reaction for the installation of the double bond and Katsuki–Sharpless asymmetric epoxidation for the introduction of chiral centers. The first total synthesis and absolute configuration assignment of heterocornol D (3a) were achieved. Four stereoisomers, 3a, ent-3a, 3b and ent-3b, of this natural polyketide were prepared, starting with 2,6-dihydroxy benzoic acid and divinyl carbinol. The absolute and relative configuration of heterocornol D was assigned via single-crystal X-ray analysis. The extension of the described synthetic approach is further presented with the synthesis of heterocornol C by applying the ether group reduction method to the lactone.
ChemInform, 2008
A facile synthesis of novel polycyclic heterocycles namely naphthaquinoxaline and naphthazaquinoxaline derivatives is carried out by the reaction of lapachol and β-lapachone, naturally occurring naphthoquinones with o-phenylene diamine and 2,3-diaminopyridine. Regioselectivity in the reaction of β-lapachone with 2,3-diaminopyridine is confirmed by single crystal X-ray diffraction of a representative compound 6,7-dihydro-8,8-dimethyl-8H-pyrano[3',2':4]-naphtha[2,1-e]pyrido[2,3b]pyrazine; C 20 H 17 N 3 O, crystallizes as orthorhombic in the space group Pbca with cell parameters a =9.793(3)Å, b=17.514(6)Å, c=18.334(6)Å, V=3144.5(17) Å 3 , Z=8,1.332 mg/m 3 , R 1 =0.3076, WR 2 =0.3595.
The Journal of Organic Chemistry, 2008
This research aimed to provide a new and "clean" synthetic method that would enable both known and novel N-heterocycles to be prepared efficiently. O-Phenyl oximes were found to be excellent precursors for iminyl radicals with a variety of acceptor side chains. Dihyropyrroles were made in good yields from O-phenyl oximes containing pent-4-ene acceptors. The analogous process with a hex-5-enyl acceptor did not yield a dihydropyridine, probably because the 6-exo-trig ring closure of the iminyl radical was too slow to compete with H-atom abstraction. The iminyl radical from a precursor with a pent-4-yne type side chain underwent ring closure followed by rearrangement to afford a pyrrole derivative. Suitably substituted iminyl radicals ring closed readily onto aromatic acceptors, thus enabling several polycyclic systems to be accessed. Quinolines were made from 3-phenylpropanones via their O-phenyl oximes. Syntheses of phenanthridines starting from 2-formylbiphenyls were particularly efficient, and this approach enabled the natural product trisphaeridine to be made. Starting from 2-phenylnicotinaldehyde derivatives, ring closures of the derived iminyl radicals onto the phenyl rings yielded benzo[h][1,6]naphthyridines. Similarly, ring closure onto a phenyl ring from a benzothiophene-based iminyl yielded a benzo[b-]thieno[2,3-c]quinoline. By way of contrast, iminyl radical ring closure onto pyridine rings was not observed. However, iminyl radicals did cyclize onto indoles, enabling indolopyridines to be prepared. The latter route was exploited in a short formal synthesis of neocryptolepine starting from 2-((1H-indol-3-yl)methyl)cyclohexanone. † University of St. Andrews. § GSK Harlow.
Chem. Heterocyclic Compds. 2013, 49, 746-759
We examined the tandem alkylation/[2+4] cycloaddition of 1-(2-furyl)-3,4-dihydroisoquinolines by various allyl halides. It was found that the process occurred through the intermediate formation of 2-allyl-1-furyl-3,4-dihydroisoquinolinium salts with a subsequent intramolecular exo addition of the allyl fragment to the furan ring. The adducts obtained were structural analogs of the isoindolo-[1,2-a]isoquinoline alkaloids jamtine and hirsutine.
Synthesis, Structure and Biological Activity of Ephedra Heterocycles
Alkaloids - Alternatives in Synthesis, Modification and Application
Ephedra compounds are well known due to their biological activity. They have been widely used in asymmetric synthesis during the last decades. Recently, we have prepared reviews about the synthesis of acyclic and heterocyclic ephedra derivative compounds reported in the literature. In this chapter, the synthetic methodology to access acyclic and heterocyclic compounds derived from ephedra alkaloids and its structural analysis are discussed, included those due to the substitution of the hydroxy group by chlorine, sulfur, selenium, or nitrogen atoms. Biological activity analysis of some synthesized compounds was done, and some of them have displayed biological activity.