Total Synthesis of (+)‐Davidiin

Kasai, Yusuke; Michihata, Naoki; Nishimura, Hidehisa; Hirokane, Tsukasa; Yamada, Hidetoshi

doi:10.1002/ange.201203305

Cited by 11 publications

(5 citation statements)

References 44 publications

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“…The 6- O pivaloyl derivative 62 gave the best stereoselectivity ( Scheme 11 ). The technique was later used in the synthesis of the natural product davidiin [ 50 ]. The 6- O -(3,5-diacetoxy-4-methoxy)benzoyl analogue of 62 was reacted with 3,5-diacetoxy-4-methoxybenzoic acid in the presence of methyl triflate, which gave the β-ester in 83% yield, showing that the principle works for ester synthesis, too.…”

Section: Reviewmentioning

confidence: 99%

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

Bols¹,

Pedersen²

2017

Beilstein J. Org. Chem.

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Silyl groups such as TBDPS, TBDMS, TIPS or TMS are well-known and widely used alcohol protective groups in organic chemistry. Cyclic silylene protective groups are also becoming increasingly popular. In carbohydrate chemistry silyl protective groups have frequently been used primarily as an orthogonal protective group to the more commonly used acyl and benzyl protective groups. However, silyl protective groups have significantly different electronic and steric requirements than acyl and alkyl protective groups, which particularly becomes important when two or more neighboring alcohols are silyl protected. Within the last decade polysilylated glycosyl donors have been found to have unusual properties such as high (or low) reactivity or high stereoselectivity. This mini review will summarize these findings.

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Section: Reviewmentioning

confidence: 99%

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

Bols¹,

Pedersen²

2017

Beilstein J. Org. Chem.

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“…A mixture of 3,4,5-tri-O-benzylgallic acid 64 (821 mg, 1.86 mmol), oxalyl chloride (360 mg, 2.84 mmol) and DMF (0.1 ml) in toluene (10 ml) was stirred for 45 min at 70°C. The reaction mixture was concentrated, and toluene (10 ml) was added to the residue.…”

Section: Nature Communications | Doimentioning

confidence: 99%

A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

et al. 2014

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Ellagitannins are a family of polyphenols containing more than 1,000 natural products. Nearly 40% of these compounds contain a highly oxygenated diaryl ether that is one of the most critical elements to their structural diversity. Here, we report a unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins. The strategy involves oxa-Michael addition of phenols to an orthoquinone building block, with subsequent elimination and reductive aromatization. The design of the building block-a halogenated orthoquinone monoketal of gallal-reduces the usual instability of orthoquinone and controls addition/elimination. Reductive aromatization is achieved with perfect chemoselectivity in the presence of other reducible functional groups. This strategy enables the synthesis of different diaryl ethers. The first total synthesis of a natural ellagitannin bearing a diaryl ethers is performed to demonstrate that the strategy increases the number of synthetically available ellagitannins.

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“…The 3 J H-H values suggested the occurrence of an axial-rich pyranose. The 1 HNMR spectra of debenzylated 4 and 2 were identical to that of 4,assynthesized by the group of Feldman, [35] and to that of natural davidiin (2), [9,10,15] respectively (see Section 3.21 and 3.22).…”

Section: Angewandte Chemiementioning

confidence: 61%

“…In particular,production of the axial-rich ellagitannins from 1 is still at the suppositional level. Fora xial chirality of the HHDP group,i ts eems that synthetic work has verified the hypothesis by showing that the couplings at the 1,6-, [15] 2,3-, [16,17] 3,4-, [18] 3,6-, [19,20] and 4,6-positions [21][22][23][24] almost reflect the axial chirality in natural products.H owever,t he verification is deficient because all reactants used in the reported work are partly galloylated glucose,w hich cannot mimic the reaction of the fully galloylated 1.A lthough as imple chemical reaction cannot reflect the biosynthesis where enzymes may take charge of the transformations,i ti si mportant to understand behaviors in non-enzymatic oxidation of 1 in the process of clarifying the biosyntheses of ellagitannins because the galloyl group can also couple non-enzymatically.However,simple oxidation of unprotected galloyl groups produces various types of reaction products,t hus making an analysis focused on the oxidation products difficult. In this study,w ei nvestigated non-enzymatic oxidation of 5 (Figure 1), an analogue of 1,and thereby reveal which 4-O-benzylated galloyl groups tended to couple…”

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confidence: 71%

“…[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%

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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 (+)‐Davidiin

Cited by 11 publications

References 44 publications

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

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

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