Recent developments in the synthesis of C-glycosides

Postema, Maarten H. D.

doi:10.1016/s0040-4020(01)89435-7

Cited by 480 publications

(135 citation statements)

References 202 publications

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“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Included in this list are aryl bromides containing electron-withdrawing and -donating substituents along with several highly substituted aromatics (see Table 1, entries [21][22][23][24].…”

Section: Stannyl-346-tri-o-(tert-butyldimethylsilyl)-o-glucal(li) Amentioning

confidence: 99%

“…Synthetic strategies directed toward the preparation of any of these classes must address not only the method of creating the key carbon-carbon bond with a large array of substituted aromatics, but also must be concerned with its stereoselective formation with respect to the various substituents at C1-C5 on the carbohydrate framework. Previously reported strategies directed toward the synthesis of C-aryl glycosides2 address, for the most part, the preparation of only one of the three main C-aryl glycoside subclasses (8).…”

Section: Introductionmentioning

confidence: 99%

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The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

Friesen¹,

Loo²,

Sturino³

1994

Can. J. Chem.

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. Can. J. Chem. 72, 1262 (I 994).The C-aryl glucals 17-31 have been prepared by the palladium-catalyzed cross coupling of l-tributylstannyl-3,4,6-tri-0-(tert-butyldimethylsily1)-D-glcal (11) and aryl bromides. The major by-product in all of these reactions is the dimer 33, the product of homocoupling of 11. Alternatively, the C-aryl glucals 34-40 can be obtained from the palladium-catalyzed coupling of l-iodo-3,4,6-tri-0-(triisopropylsilyl)-~-glucal (16) and a variety of metalated aromatics, including ArZnC1, ArB(OH),, and ArB(OMe),. The advantages of the latter procedure include superior coupling yields under milder reaction conditions and the high yielding preparation of 16 directly from 3,4,6-tri-0-(triisopropylsily1)-D-glucal (12) by a metalation-iodination sequence.RICHARD W. FRIESEN, RICHARD W. LOO et CLAUDIO F. S m o . Can. J. Chem. 72, 1262Chem. 72, (1994.On a prCparC les C-aryl glucals 17-31 par un couplage croisC catalysC par le palladium du 1-tributylstannyl-3,4,6-tri-0-(tert-butyldimCthylsily1)-D-glucal (11) et des brornures d'aryle. Le sous-produit principal de toutes ces rkactions est le dimkre 33, le produit d'homocouplage du produit 11. On peut aussi obtenir les C-aryl glucals 34-40 par un couplage catalysC par le palladium du 1-iodo-3,4,6-tri-0-(triisopropylsilyl)-~-glucal (16) avec une variktC de produits aromatiques mCtallCs comportant le ArZnC1, le ArB(OH), et ArB(OMe),. Les avantages de la dernikre mCthode incluent des rendements supCrieurs de couplage dans des conditions plus douces et la pr~paration avec un rendement Clevk du composC 16 directement 2 partir du 3,4,6-tri-0-(triisopropylsily1)-D-glucal (12) par une sequence de metallation et d'iodation.[Traduit par la RCdaction]

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Section: Stannyl-346-tri-o-(tert-butyldimethylsilyl)-o-glucal(li) Amentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

Friesen¹,

Loo²,

Sturino³

1994

Can. J. Chem.

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“…[1,2] In recent times, indium halides have emerged as versatile Lewis acid catalysts imparting high regio-, chemo-, and diastereoselectivity to a variety of organic transformations.[3] Compared to conventional Lewis acids, indium tribromide, in particular, has advantages of low catalyst loading, moisture stability, and catalyst recycling.[4] C-Glycosides bearing carbon-linked heterocycles have attracted great attention owing to their potent antiviral and antitumor behavior.[5] Because of these properties of aryl glycosides, we have attempted C-glycosidation with aryl amines to synthesize aryl C-glycosides with a free amino functionality for further derivatization. Interestingly, we observed for the first time an unusual formation of benzofused heterobicycles in the aminoglycosidation.…”

mentioning

confidence: 99%

InBr₃‐Catalyzed Cyclization of Glycals with Aryl Amines

et al. 2003

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Dedicated to Professor Goverdhan Mehta on the occasion of his 60th birthdayGlycals are ambident electrophiles capable of reacting with various nucleophiles such as alcohols, malonates, and silyl nucleophiles under the influence of acid catalysts or oxidants to produce 2,3-unsaturated glycosides. [1,2] In recent times, indium halides have emerged as versatile Lewis acid catalysts imparting high regio-, chemo-, and diastereoselectivity to a variety of organic transformations.[3] Compared to conventional Lewis acids, indium tribromide, in particular, has advantages of low catalyst loading, moisture stability, and catalyst recycling.[4] C-Glycosides bearing carbon-linked heterocycles have attracted great attention owing to their potent antiviral and antitumor behavior.[5] Because of these properties of aryl glycosides, we have attempted C-glycosidation with aryl amines to synthesize aryl C-glycosides with a free amino functionality for further derivatization. Interestingly, we observed for the first time an unusual formation of benzofused heterobicycles in the aminoglycosidation.In our continuing research on glycoside synthesis, [6] we have made unprecedented observations in the aminoglycosidation reactions of glycals with aryl amines, which we report here. Initially, we attempted the aminoglycosidation reaction of d-glucal with aniline using 10 mol % indium(iii) bromide as a novel glycosyl activator. Interestingly, the unusual bicyclic adduct 3 a (R = H) was isolated in 85 % yield with high stereoselectivity (Scheme 1).The product 3 a was characterized thoroughly by various NMR experiments including double-quantum-filtered correlation spectroscopy (DQFCOSY), nuclear Overhauser effect spectroscopy (NOESY), heteronuclear single-quantum correlation spectroscopy (HSQC), [7] and 3 J CH -optimized HMBC experiments.[8] The edited HSQC spectrum showed the presence of two methylene groups in addition to eight methine and two methyl groups. The location of the methylene group in the bridge of a bicyclononene-like structure was confirmed by the presence of small couplings between these protons and the bridgehead protons H1 and H3 (J H1-H2(pro-S) = 3.7 Hz, J H1-H2(pro-R) = 1.8 Hz, J H2(pro-S)-H3 = 2.4 Hz, and J H2(pro-R)-H3 = 4.6 Hz; Figure 1)). Fusion of the bicyclononene and the aromatic ring at C1ÀC11 and NHÀC3 was confirmed by nOe interactions between H1 and H12. Further support for the structure came from HMBC peaks for H1/C12, H1/C11, H1/C16 and H12/C1. The two six-membered rings of the bicyclononane moiety have two different conformations. The one containing oxygen takes a chair form,

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“…to these methods are that they rely on the generation of unstable boron dihalide species thereby resulting in low functional group tolerance. The number of methodologies for the preparation of C-glycosides has increased tremendously over the past several decades due their presence in natural products and enzymatically stable analogs of pharmaceutical importance [17][18][19][20][21][22][23][24][25][26]. In particular, the synthesis of 2-alkenyl and 2-alkynyl tetrahydrofuran products has been relatively well explored.…”

Section: Resultsmentioning

confidence: 99%

Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

Fisher

Bolshan

2016

Catalysts

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Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species, thereby resulting in low functional group tolerance. Recently, we discovered that in the presence of a Brønsted acid, trifluoroborate salts react rapidly with in situ generated oxocarbenium ions. Here, we report Brønsted acid-catalyzed direct substitution of 2-ethoxytetrahydrofuran using potassium trifluoroborate salts. The reaction occurs when tetrafluoroboric acid is used as a catalyst to afford functionalized furans in moderate to excellent yields. A variety of alkenyl-and alkynyltrifluoroborate salts readily participate in this transformation.

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Recent developments in the synthesis of C-glycosides

Cited by 480 publications

References 202 publications

The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

InBr₃‐Catalyzed Cyclization of Glycals with Aryl Amines

Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

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Recent developments in the synthesis of C-glycosides

Cited by 480 publications

References 202 publications

The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

InBr3‐Catalyzed Cyclization of Glycals with Aryl Amines

Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

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InBr₃‐Catalyzed Cyclization of Glycals with Aryl Amines