A general, efficient, and common strategy for the synthesis of (-)-juglomycin A, (+)-kalafungin, (+)-frenolicin B, and (+)-deoxyfrenolicin is reported here. The strategy involves the synthesis of a key building block alkyne from a cheap chiral pool material, D-glucono-δ-lactone, Dötz benzannulation, oxa-Pictet-Spengler reaction, and H(2)SO(4)-mediated epimerization.
A variety of 3-aryl tetronic acids have been synthesized by an undirected, intermolecular C-H functionalization of arenes with 3-diazofuran-2,4-dione. This methodology featured as a key step in the synthesis of a series of naturally occurring 3-aryl-5-arylidene tetronic acids (pulvinates) from commercially available tetronic acid. Salient features of the pulvinic acid synthesis include a one-step, stereoselective synthesis of the C5 arylidene group and a single step introduction of the C3 aryl substituent.
Concise syntheses of the polyketide natural product (–)-muricatacin and (–)-(R,R)-L-factor (natural product enantiomer) were achieved in four steps by employing an organocatalytic asymmetric direct vinylogous aldol reaction of γ-crotonolactone and suitable aliphatic aldehydes as the key step.
A modular synthesis of aspulvinones A, B, C, D, E, G and the recently isolated aspulvinone Q was developed. The methodology features a highly stereoselective aldol condensation of diazotetronic acid with aldehydes to provide 5-arylidene diazotetronates. Subsequent catalytic intermolecular C-H insertion reactions of the arylidene tetronates with arenes provide a series of naturally occurring aspulvinones including aspulvinones C, D and Q which have not been synthesized before. Variation of the aldehyde and the arene components furnishes synthetic analogues of the aspulvinones.
The synthesis of novel nucleoside analogues bearing a C3′ all-carbon quaternary center and a C2′-hydroxy substituent is described. The all-carbon stereogenic center was generated through an intramolecular 7-endo attack of a silyltethered allyl moiety on a tertiary radical using photoredox catalysis. Subsequent allylic oxidation and diastereoselective hydride reductions provided the hydroxy substituent at C2′, which then controls the stereoselective introduction of pyrimidine nucleobases on the corresponding furanose scaffold. Density functional theory (DFT) calculations provided insights into the origin of the high syn diastereoselectivity resulting from the radical cyclization. This original methodology grants access to a wide range of 1′,2′-cis and 1′,2′-trans arabino-and ribo-like analogues bearing an all-carbon quaternary center at C3′. These molecules are currently being tested for their antiviral and anticancer properties.
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