A reference electrode equipped with ionic liquid salt bridge consisting of tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide has been employed for potentiometric precipitation ...titration of chloride with silver ions in water at 25 °C. A model for the titration curve was regressed to experimental curves, taking into account the change in the activity coefficients of relevant ionic species in the course of the titration, to obtain the least square estimates of two adjustable parameters in the model, the solubility product (Ksp) and the analyte concentration. The least-square estimate of Ksp, (1.840 ± 0.060) × 10−10, i.e., pKsp = 9.736 ± 0.014, is in good agreement with literature data, but with higher precision.
The first total synthesis of a marine natural product, exigurin, has been accomplished in 13 steps starting from (+)-menthone. The key intermediate (−)-10-
epi
-axisonitrile-3 was prepared by ...stereoselective intramolecular cyclopropanation followed by a cyclopropane ring opening reaction by the azide anion. The bioinspired Ugi reaction of (−)-10-
epi
-axisonitrile-3, formaldehyde, sarcosine and methanol successfully constructed the target exigurin in which its terpene and amino acid units were linked through an amide bond.
Bioinspired U-5C-4CR employing (−)-10-
epi
-axisonitrile-3, formaldehyde and sarcosine in methanol showed remarkable efficiency to assemble multicomponents in a one-pot process, leading to the first total synthesis of exigurin.
A reference electrode equipped with ionic liquid salt bridge consisting of tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide has been employed for potentiometric precipitation ...titration of chloride with silver ions in water at 25 °C. A model for the titration curve was regressed to experimental curves, taking into account the change in the activity coefficients of relevant ionic species in the course of the titration, to obtain the least square estimates of two adjustable parameters in the model, the solubility product (Ksp) and the analyte concentration. The least-square estimate of Ksp, (1.840 ± 0.060) × 10−10, i.e., pKsp = 9.736 ± 0.014, is in good agreement with literature data, but with higher precision.
A highly diastereoselective and enantioselective method for the asymmetric desymmetrization of 4,4-disubstituted cyclohexadienones using the Michael addition reaction of malonates under catalysis ...with the primary amine-thiourea conjugate catalyst and PPY at high pressure was developed.
Total synthesis of (−)-agelastatin A has been achieved starting from l-arabitol. The highlights in our synthesis include the preparation of vicinal diamine moiety by 3.3 sigmatropic rearrangement of ...allyl cyanate and construction of central ring-C with ring-closing metathesis.
A new method for chiral diamine-catalyzed Robinson-type annulation was developed to construct cyclohexenone derivatives bearing a quaternary carbon stereogenic center at the 4-position in high ...enantiomeric excess. This method was successfully applied to the short synthesis of (+)-sporochnol A.
A new route for the synthesis of the cytotoxic anhydrosphingosine pachastrissamine has been developed. 3.3 Sigmatropic rearrangement of an allyl cyanate was employed to construct the allyl amine ...moiety in
2 from the chiral C-4 unit
3. Oxidative cleavage of the double bond in
2, followed by THF ring formation furnished the target pachastrissamine.
A new route for the synthesis of cytotoxic anhydrosphingosine pachastrissamine has been established using 3.3 sigmatropic rearrangement of allyl cyanate.
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The first nonracemic synthesis of (+)-geranyllinaloisocyanide, starting with (–)-lactic acid methyl ester, has been accomplished by exploiting a 3.3 sigmatropic rearrangement of allyl cyanate. The ...synthesis enables assignment of the S configuration of the C(3) isocyano substituted, quaternary stereogenic center in natural geranyllinaloisocyanide.
A pathway for the biosynthesis of halichonadin G involving the unique action of ugiase and isocyanide oxidase is proposed. This hypothesis was tested in a biomimetic approach to the synthesis of the ...core structural unit of this marine sponge terpene, which relies on a key Ugi coupling reaction and an isocyanide‐to‐isocyanate oxidative transformation. The results of this effort demonstrate that the biomimetic strategy can be employed to construct the core structure of halichonadin G in an efficient manner.
A unique pathway for the biosynthesis of the marine sponge terpene halichonadin G is proposed. On the basis of this proposal, a biomimetic approach involving a Ugi coupling reaction is designed and applied to the efficient construction of the core structure of halichonadin G.
