Total Synthesis of Ellagitannins through Regioselective Sequential Functionalization of Unprotected Glucose

Takeuchi, Hironori; Mishiro, Kenji; Ueda, Y.; Fujimori, Yusuke; Furuta, Takumi; Kawabata, Takeo

doi:10.1002/ange.201500700

Cited by 23 publications

(15 citation statements)

References 32 publications

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“…We previously proposed a possible mechanism for the highly selective monoacylation of polyol compounds, [18][19][20][21][22][23][24][25][26][27] involving hydrogen bonding between the amide oxygen of catalyst 6 and the relatively acidic hydroxy group of the substrate. We therefore suspected that the C-7-allylic alcohol may take a hydrogen bond with the amide group of catalyst 6.…”

Section: Resultsmentioning

confidence: 99%

“…catalyst 6, which was effective for the site-selective monoacylation of polyol compounds such as glycopyranoses, [18][19][20][21][22][23][24] linear diols, 25) tri-and tetra-substituted α,α′-alkenediols, 26,27) 2-aminopentane-1,5-diol derivatives, 28) and 10-deacetylbaccatin III. 29) The amide oxygen of catalyst 6 acted as a Brøn-sted base to allow hydrogen bonding with the relatively acidic hydroxy group of the substrate, thus inducing selective acylation of the adjacent hydroxy group.…”

Section: This Article Is Dedicated To Professor Satoshi ōMura In Celementioning

confidence: 99%

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Organocatalytic Site-Selective Acylation of Avermectin B<sub>2a</sub>, a Unique Endectocidal Drug

Yamada

Suzuki

Hirose

et al. 2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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The organocatalytic site-selective monoacylation of avermectin B 2a , an insecticidal and anti-parasitic drug, was accomplished. Although an acetylation of avermectin B 2a using a 4-dimethylaminopyridine (DMAP) as a catalyst gave poor site-selectivity, use of our organocatalyst increased site-selectivity of the acylation at the C-5-OH as well as the yield of monoacetate. This catalyst was also effective in other acylations. Interestingly, trihaloacetylation under same conditions gave poor site-selectivity. However, the use of an enantiomer of our organocatalyst provided the C-4″-O-trihaloacetyl avermectin B 2a with excellent siteselectivity. These results indicate that the site-selective acylation of avermectin B 2a can be controlled by the combination of a suitable organocatalyst and an acid anhydride.

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Section: Resultsmentioning

confidence: 99%

Section: This Article Is Dedicated To Professor Satoshi ōMura In Celementioning

confidence: 99%

Organocatalytic Site-Selective Acylation of Avermectin B<sub>2a</sub>, a Unique Endectocidal Drug

Yamada

Suzuki

Hirose

et al. 2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…140 Upon treatment of saccharide 79 with anhydride 80 in the presence of catalyst 73 , selective C4′ acylation yields 81 in 91% yield. At this stage, the C6′–OH is the most reactive alcohol, and this can be coupled to carboxylic acid 82 in a site-selective ester-ification to yield 83 .…”

Section: Group Transfer To Hydroxyl Groupsmentioning

confidence: 99%

Applications of Nonenzymatic Catalysts to the Alteration of Natural Products

2017

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The application of small molecules as catalysts for the diversification of natural product scaffolds is reviewed. Specifically, principles that relate to the selectivity challenges intrinsic to complex molecular scaffolds are summarized. The synthesis of analogs of natural products by this approach is then described as a quintessential “late-stage functionalization” exercise wherein natural products serve as the lead scaffolds. Given the historical application of enzymatic catalysts to the site-selective alteration of complex molecules, the focus of this review is on the recent studies of non-enzymatic catalysts. Reactions involving hydroxyl group derivatization with a variety of electrophilic reagents are discussed. C–H bond functionalizations that lead to oxidations, aminations, and halogenations are also presented. Several examples of site-selective olefin functionalizations and C–C bond formations are also included. Numerous classes of natural products have been subjected to these studies of site-selective alteration including polyketides, glycopeptides, terpenoids, macrolides, alkaloids, carbohydrates and others. What emerges is a platform for chemical remodeling of naturally occurring scaffolds that targets virtually all known chemical functionalities and microenvironments. However, challenges for the design of very broad classes of catalysts, with even broader selectivity demands (e.g., stereoselectivity, functional group selectivity, and site-selectivity) persist. Yet, a significant spectrum of powerful, catalytic alterations of complex natural products now exists such that expansion of scope seems inevitable. Several instances of biological activity assays of remodeled natural product derivatives are also presented. These reports may foreshadow further interdisciplinary impacts for catalytic remodeling of natural products, including contributions to SAR development, mode of action studies, and eventually medicinal chemistry.

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“…[20] This coupling reaction was suitable for as tudy aimed at understanding the non-enzymatic oxidation of the b-PGG analogue because 1) the reaction proceeds effectively at room temperature,w hen thermal conditions are similar to those of the biosynthesis,2 )the spatial proximity of the groups to each other make coupling possible,a nd 3) the reaction has been applied in syntheses of natural ellagitannins for coupling of the galloyl groups at various positions of glucose. [15,18,[24][25][26][27][28] Theo xidation of 5 with CuCl 2 and n BuNH 2 provided ac omplicated mixture of products ( Figure 2). We conducted the reaction, after optimization to completely consume 5, because residual reactant would make separation of the products increasingly difficult.…”

Section: Angewandte Chemiementioning

confidence: 99%

Non‐Enzymatic Oxidation of a Pentagalloylglucose Analogue into Members of the Ellagitannin Family

et al. 2017

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The occurrence of more than 1000 structurally diverse ellagitannins has been hypothesized to begin with the oxidation of penta-O-galloyl-β-d-glucose (β-PGG) for the coupling of the galloyl groups. However, the non-enzymatic behavior of β-PGG in the oxidation is unknown. Disclosed herein is which galloyl groups tended to couple and which axial chirality was predominant in the derived hexahydroxydiphenoyl groups when an analogue of β-PGG was subjected to oxidation. The galloyl groups coupled in the following order: at the 4,6-, 1,6-, 1,2-, 2,3-, and 3,6-positions with respective S-, S-, R-, S-, and R-axial chirality. Among them, the most preferred 4,6-coupling reflected the what was observed for natural ellagitannins. A new finding was that the second best coupling occured at the 1,6-positions. With the detection of a 3,6-coupled product, this work demonstrated that even ellagitannin skeletons with an axial-rich glucose core may be generated non-enzymatically.

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Total Synthesis of Ellagitannins through Regioselective Sequential Functionalization of Unprotected Glucose

Cited by 23 publications

References 32 publications

Organocatalytic Site-Selective Acylation of Avermectin B<sub>2a</sub>, a Unique Endectocidal Drug

Organocatalytic Site-Selective Acylation of Avermectin B<sub>2a</sub>, a Unique Endectocidal Drug

Applications of Nonenzymatic Catalysts to the Alteration of Natural Products

Non‐Enzymatic Oxidation of a Pentagalloylglucose Analogue into Members of the Ellagitannin Family

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