The rare benzoxazepine ring in the alkaloid inducamide C is unstable and prone to rearrangement, indicating that structural revision of the natural product may be necessary.
<div>Here, we newly propose the structure of protoaculeine B, an N-terminal moiety of the marine peptide toxin aculeine B, as possessing the cis-disubstituted tetrahydro-beta-carboline framework. We prepared two truncated model compounds that lack long-chain polyamine by one-step Pictet-Spengler reaction of tryptophan, and compared the NMR and mass spectra and chemical reactivity with those of natural protoaculeine B. The synthetic models reproduced the profiles of the natural product well, which was conclusive for the structural revision.</div>
We report the first total
synthesis of (+)-granatumine A, a limonoid alkaloid with PTP-1B inhibitory
activity, in 10 steps. Over the course of this study, two key methodological
advances were made: a cost effective
procedure for ketone alpha,beta-dehydrogenation using allyl-Pd catalysis, and a Pd-catalyzed protocol to
convert epoxyketones to 1,3-diketones. The central tetrasubstituted pyridine is
formed by a convergent Knoevenagel condensation and carbonyl-selective electrocyclization
cascade, which was followed by a direct transformation of a 2<i>H</i>-pyran to a pyridine. These studies
have led to the structural revision of two members of this family.
Solid-Phase Stereocontrolled Synthesis of Oligomeric P-Modified Glycosyl Phosphate Derivatives Using the Oxazaphospholidine Method
