Towards the synthesis of streptovaricin D: Synthesis of fully elaborated aromatic precursors and coupling with ansa chain fragments
作者:William R. Roush、David J. Madar
DOI:10.1016/0040-4039(93)85004-g
日期:1993.3
The highly functionalized streptovaricin-damavaricin D aromaticprecursors 12 and 15 have been prepared and coupled with propionaldehyde or unsaturated aldehydes 16 and 18 via aryllithium intermediates to give 2, 3 and 19.
[3 + 4] and [3 + 5] Annulation Reactions of .alpha.-(Phenylthio)Dicarbonyl Electrophiles with Bis(trimethylsilyl) Enol Ethers: Synthesis of Highly Functionalized Medium Ring Carbocycles
作者:Gary A. Molander、Paul R. Eastwood
DOI:10.1021/jo00131a013
日期:1995.12
The [3 + 4] and [3 + 5] annulations of bis(trimethylsilyl) enol ethers with 1,4- and 1,5-dicarbonyl electrophiles bearing alpha-phenylthio substituents leads to the formation of bicyclic [3.2.1] and [3.3.1] ethers with good regiochemical and stereochemical control, Subsequent oxidation of the phenylthio moiety followed by reduction with SmI2 constitutes a high-yielding and regioselective process for cleavage of the bridging ether linkage. The overall strategy provides a synthetic pathway for the synthesis of highly functionalized medium ring carbocycles.
Synthesis of specifically O-alkylated anthraquinones by cycloaddition
作者:Donald W Cameron、Geoffrey I Feuitrill、Glenn B Gamble、John Stavrakis
DOI:10.1016/s0040-4039(00)85117-5
日期:1986.1
Synthesis of highly functionalized naphthoate precursors to damavaricin D Observation of kinetically stable benzocyclohexadienones in the bromination reactions of highly functionalized β-naphthol derivatives
作者:William R. Roush、David J. Madar、D. Scott Coffey
DOI:10.1139/cjc-79-11-1711
日期:——
Selective syntheses of the highly substituted bromonaphthoates 4a, 4b, 19, and 22 are reported. These compounds were targeted as precursors to the naphthoquinone nucleus of damavaricin D; compound 22 ultimately was used in the successful total synthesis. The synthesis of 22 features the Diels-Alder reaction of the oxygenated diene 5 and 2,6-dibromo-3-methylbenzoquinone 6 to establish the core naphthalenic unit. The quinone was protected throughout this synthesis as a 1,4-bis-methoxymethyl-1,4-dihydroquinone (see 36). The C-2-carboalkoxy group of 22 was added by carboxylation of the aryllithium intermediate generated from 36, and protected as a beta -trimethylsilylethyl ester. Finally, the C-8-Br substituent was introduced by NBS bromination of 38. This reaction proceeds by way of bromobenzocyclohexadienone 39. Related bromobenzo-cyclohexadienones 13 and 29 were observed in the NBS brominations of the highly functionalized beta -naphthyl MOM ethers 11 and 28. The bromobenzocyclohexadienones 29 and 39 undergo facile substitution reactions with chloride ion and reduction with bromide ion at rates competitive with base-promoted aromatization. The surprising kinetic stability of these intermediates is attributed to a combination of steric and stereoelectronic factors.
Dichloro quinones as dienophiles: synthesis of alizarin derivatives
作者:Donald W. Cameron、Geoffrey I. Feutrill、Philip L.C. Keep