Reaction of 6-chloro-2-fluoro-3-pyridineacetamide with 1,2-bis(trimethylsilyloxy)cyclobutene in ether saturated with hydrogen chloride afforded the keto amide in 85% yield. In the key step, treatment of the keto amide with aqueous KOH in t-BuOH resulted In a tandem intramolecular aldol reaction-intramolecular nucleophilic aromatic substitution sequence to give the tetracylic lactam In 46% yield. Reduction of the lactam with BH3 In THF gave phantasmidine in 67% yield.
Mosher's Amide-Based Assignment of the Absolute Configuration of Phantasmidine
作者:Barry B. Snider、Quan Zhou
DOI:10.3987/com-13-s(s)45
日期:——
The absolute configuration of phantasmidine was assigned by analysis of the two conformers of the two Mosher amides. The expected shielding of the protons adjacent to the nitrogen and large long range shielding (similar to 1 ppm) of the cyclobutane methylene protons in 16major and the pyridine protons of 16minor by the phenyl group of the Mosher amide allows the assignment of absolute configuration as shown in Schemes 4 and 5.