Cyclodepsipeptide alveolaride C: total synthesis and structural assignment

Stereoselective synthesis of thailandamide A methyl ester

A convergent strategy for the stereoselective synthesis of the methyl ester of the structurally challenging and highly labile antibacterial polyene polyketide natural product thailandamide A has been developed. The key steps include the Zincke aldehyde reaction, Stille cross coupling, Negishi reaction, Julia-Kocienski olefination, cross metathesis, and the less explored Pd(I)-based Heck coupling to access different unsaturation bonds. Additionally, Urpi acetal aldol, Evans methylation, and Crimmins acetate aldol reactions were employed to construct four out of six asymmetric centers of the molecule.

Total Synthesis of Antibacterial Macrolide Sorangiolide A

A convergent route for the asymmetric total synthesis of antibacterial macrolide sorangiolide A has been developed for the first time. The key feature of this synthesis includes Krische iridium-catalyzed anti-diastereoselective carbonyl crotylation, Crimmins acetate aldol, Yamaguchi esterification, Julia-Kocienski olefination, Horner-Wadsworth-Emmons olefination, and ring-closing metathesis. The origin of the low intensity of the 13C{1H} NMR signals of the C1 and C2 centers of the natural product has been investigated, disclosing possible forms of existence for the natural product in the solution phase.

Sharpless Asymmetric Dihydroxylation: An Impressive Gadget for the Synthesis of Natural Products: A Review

Sharpless asymmetric dihydroxylation is an important reaction in the enantioselective synthesis of chiral vicinal diols that involves the treatment of alkene with osmium tetroxide along with optically active quinine ligand. Sharpless introduced this methodology after considering the importance of enantioselectivity in the total synthesis of medicinally important compounds. Vicinal diols, produced as a result of this reaction, act as intermediates in the synthesis of different naturally occurring compounds. Hence, Sharpless asymmetric dihydroxylation plays an important role in synthetic organic chemistry due to its undeniable contribution to the synthesis of biologically active organic compounds. This review emphasizes the significance of Sharpless asymmetric dihydroxylation in the total synthesis of various natural products, published since 2020.

Stage-specific and cell type-specific requirements of ikzf1 during haematopoietic differentiation in zebrafish

The zinc finger transcription factor Ikaros1 (Ikzf1) is required for lymphoid development in mammals. Four zinc fingers constitute its DNA binding domain and two zinc fingers are present in the C-terminal protein interaction module. We describe the phenotypes of zebrafish homozygous for two distinct mutant ikzf1 alleles. The IT325 variant lacks the C-terminal two zinc fingers, whereas the fr105 variant retains only the first zinc finger of the DNA binding domain. An intact ikzf1 gene is required for larval T cell development, whereas low levels of adult lymphoid development recover in the mutants. By contrast, the mutants exhibit a signature of increased myelopoiesis at larval and adult stages. Both mutations stimulate erythroid differentiation in larvae, indicating that the C-terminal zinc fingers negatively regulate the extent of red blood cell production. An unexpected differential effect of the two mutants on adult erythropoiesis suggests a direct requirement of an intact DNA binding domain for entry of progenitors into the red blood cell lineage. Collectively, our results reinforce the biological differences between larval and adult haematopoiesis, indicate a stage-specific function of ikzf1 in regulating the hierarchical bifurcations of differentiation, and assign distinct functions to the DNA binding domain and the C-terminal zinc fingers.

Total synthesis of the antibacterial polyketide natural product thailandamide lactone

Stereoselective total synthesis of the structurally intriguing polyketide natural product thailandamide lactone was accomplished, and done so using a convergent approach for the first time to the best of our knowledge. The key features of this synthesis included use of a Crimmins acetate aldol reaction, Evans methylation, Urpi acetal aldol reaction, Sharpless asymmetric epoxidation and subsequent γ-lactonization for the installation of six asymmetric centers and the use of the Negishi reaction, Julia-Kocienski olefination, cross metathesis, HWE olefination and intermolecular Heck coupling for construction of a variety of unsaturated linkages. Pd(i)-based Heck coupling was introduced, for the first time to the best of our knowledge, quite efficiently to couple the major eastern and sensitive western segments of the molecule. The antibacterial activity of thailandamide lactone was also evaluated.

Late-Stage Functionalization: Total Synthesis of Beauveamide A and Its Congeners and Their Anticancer Activities

Asymmetric total synthesis of cyclotetradepsipeptide beauveamide A has been achieved for the first time. A macrolactamization strategy involving two possible sites has been explored to find the most effective route for cyclization. A late-stage functionalization approach has been adopted for easy access of non-natural analogues of beauveamide A for further biological evaluation. Interestingly, the anticancer activity of one of the synthesized analogues was better than that of the parent natural product.

Total Synthesis of Strasseriolide A

Stereoselective total synthesis of structurally intriguing antimalarial macrolide strasseriolide A has been accomplished by adopting a convergent approach. The salient features of this synthesis include Co(BH₄)₂-mediated selective reduction of conjugated olefin, Crimmins propionate aldol, Evans alkylation, intermolecular Horner-Wadsworth-Emmons olefination, Yamaguchi macrolactonization, and selective saponification of ester moiety in the presence of a lactone functionality. The ¹³C{¹H} NMR data of strasseriolide A were found to be very sensitive to its solution concentration.

Total synthesis and stereochemical assignment of bipolamide A acetate

Asymmetric total synthesis of an acetate analogue of the endophytic unstable secondary metabolite bipolamide A has been achieved for the first time adopting a convergent approach. The key feature of this synthesis includes Evans's asymmetric ethylation, Wittig olefination, Takai olefination, stereoselective Grignard addition and intermolecular Heck coupling. This eventually developed a synthetic route of the rarely found branched amine bearing an acyloin moiety. Our synthesis finally established unambiguously the stereochemistry of the unassigned C-8 center of the naturally occurring unstable bipolamide A.

Total Synthesis and Assignment of the Absolute Configuration of (+)-Omphalic Acid

Omphalane diterpenoids usually contain a cyclohexane-fused bicyclo[3.2.1]octane scaffold embedded with two continuous quaternary carbon centers, which pose considerable challenges to synthetic chemists. Herein, we reported the first total synthesis of omphalic acid with high stereochemical control, featuring an intermolecular Diels-Alder cycloaddition, ring reorganization through Criegee oxidative cleavage and programmed aldol condensations, conformationally controlled hydrogenation, and Pd-catalyzed carboxylation. The absolute configuration of omphalic acid was defined for the first time via the asymmetric total synthesis facilitated by a derivatization resolution protocol.

Asymmetric Total Synthesis of Amphirionin-2

A convergent route for the asymmetric total synthesis of potent anticancer polyketide natural product amphirionin-2 has been developed. Our initial synthetic trials revealed that the proposed structures of amphirionin-2 need to be revised consistent with a recent report of Fuwa et al., where the actual structure of amphirionin-2 was established. The key features of our synthesis comprised Sharpless asymmetric dihydroxylation, followed by cycloetherification, Wittig olefination, Julia-Kocienski olefination, and Crimmins propionate aldol reaction.