A concise and stereocontrolled first total synthesis of Ivorenolide A (1) is reported in 16 longest linear steps with a 13.4% overall yield starting from (+)-diethyl tartrate (DET). Key features are base-induced elimination protocol for the construction of chiral propargyl alcohols in both fragments, Pd-catalyzed cross-coupling of terminal acetylenes, and Shiina's 2-methyl-6-nitrobezoic anhydride (MNBA) mediated macrolactonization.
Three chloroaluminate
ionic liquids (ILs), triethylammonium
tetrachloroaluminate ([HN222][AlCl4]), triethylammonium
heptachlorodialuminate ([HN222][Al2Cl7]), and tetraethylammonium heptachlorodialuminate ([N2222][Al2Cl7]), were employed to investigate liquid
clathrate (LC) formation and the relative role of the cation or anion
in aromatic solubility. The trend in molar solubilities in all three
ILs was found to be benzene > toluene > o-xylene
> p-xylene ∼ m-xylene
> mesitylene;
however, the solubilities in the [AlCl4]− IL were 40–70% lower than those found for the two [Al2Cl7]− ILs, which were nearly
equivalent. Attempts to crystallize analogues of the LC phases from
aromatic solutions of [N2222][Al2Cl7] led to crystalline [N2222][Al2Cl7]·C6H6 from benzene and [N2222][AlCl4] from all other aromatic solvents. NMR analyses
of [HN222][AlCl4] and [HN222][Al2Cl7] LCs supported the crystallographic analyses,
where 27Al NMR confirmed the dynamic speciation of the
[Al2Cl7]− anions but not the
[AlCl4]− anions, and 1H NMR
supported the crystallographic observation that each benzene interacts
with two cations; however, the solution data suggested a 2:1 benzene/IL
ratio.
Synthesis of enantiomerically pure propargyl alcohols is one of the most important tools in organic synthesis and “base-induced elimination of β-alkoxy chlorides” could offer the enantiomerically pure propargyl alcohols.
A synergistic dual catalysis approach involving gold and copper catalysts for the synthesis of macrolactones bearing 1,3‐butadiynes through an intramolecular Glaser–Hay coupling reaction in good yield is described. This dual catalytic system exhibited good selectivity, reactivity and functional group tolerance. This unique process offers a paradigm shift: the potential as well as the versatility of this novel method is not only exemplified for the synthesis of macrolactones of different ring size but also for the rapid total synthesis of ivorenolide B, a new class of macrolides endowed with conjugated 1,3‐diyne motif, having impressive immunosuppressive activities.
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