Fremy’s Salt-Mediated Oxidative Addition. A New Approach in the Total Synthesis of Naturally Dipetalolactone and Its Immunomodulatory Activity

Abstract

Abstract:The structure of the natural dipyranocoumarin dipetalolactone has been confirmed by an unambiguous synthetic route from resorcinol. This sequence was initiated by a pyran ring formation step which introduced the 3-chloro-3-methylbut-1-yne moiety. Then, the expected product undergoes a Fremy's salt-meditated oxidative addition followed by ring closure to yield dipetalolactone. Dipetalolactone was also found to have immunological activity in a mouse carcinoma S180-bearing mice cell line.

Two New Benzoquinone Derivatives from Vietnamese Knema globularia Stems

“…The ether linkage between C-2 and C-8a was determined based on the chemical shift values of C-2 and C-8a (δ C 81.2 and 154.0, respectively) and those of 2,2-dimethyl-2H-chromene-5,7,8(6H)trione. [10] Thus, compound 1, identified as embenone A or 2,2,4trimethyl-6-hydroxychromene-7-pentadecanyl-5,8-dione, was depicted in Figure 1.…”

“…Furthermore, the spin system through C‐9‐C‐4‐C‐3‐C‐2(C‐11)‐C‐10 and C‐4‐C‐4a‐C‐8a‐C‐8 could be deduced from the HMBC correlations (Figure 2). The ether linkage between C‐2 and C‐8a was determined based on the chemical shift values of C‐2 and C‐8a ( δ C 81.2 and 154.0, respectively) and those of 2,2‐dimethyl‐2 H ‐chromene‐5,7,8(6 H )‐trione [10] . Thus, compound 1 , identified as embenone A or 2,2,4‐trimethyl‐6‐hydroxychromene‐7‐pentadecanyl‐5,8‐dione, was depicted in Figure 1.…”

A One‐Pot Synthesis of Pyranocoumarins Through Microwave‐Promoted Propargyl Claisen Rearrangement/Wittig Olefination

“…Recent syntheses of pyranocoumarins, inter alia seselin ( 8 ), involve catalyst‐free multicomponent or two‐step condensation reactions that start from phloroglucinol, ring‐closing metathesis reactions at preformed coumarin scaffolds, cobalt‐catalyzed cyclizative carbonylations of vinylphenols, cyclizative Wittig olefinations of 6‐formyl chromenes, or oxidative selenium‐mediated cyclizations of prenylated hydroxycoumarins . Most syntheses of seselin and structurally related angular pyranocoumarins are prepared from preformed coumarins, either by thermal propargyl Claisen rearrangements of the corresponding coumarin 2,2‐dimethylpropargyl ethers, or by acid‐catalyzed condensations of hydroxycoumarins and acetals of senecialdehyde . Microwave conditions have been used only in a limited number of pyranocoumarin syntheses.…”