Organotin derivatives and the selective acylation and alkylation of the equatorial hydroxy group in a vicinal, equatorial-axial pair

Nashed, Mina A.; Anderson, Louise E.

doi:10.1016/s0040-4039(00)71342-6

Cited by 129 publications

(25 citation statements)

References 9 publications

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“…The deshielded positions of the C-3 signals in the 13 C NMR spectra, assigned via COSY and HSQC experiments, established the structures of these products unambiguously. It is very well known that alkylation reactions performed on dibutylstannylene acetals derived from cis-diols on six-membered rings results in alkylation on the equatorial oxygen atom 13,14,25,26 and the current results extend the structures of the alkylating agents used to long-chain alkyl bromides.…”

Section: Resultssupporting

confidence: 63%

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl β-d-galactopyranoside and derivatives via dibutylstannylene acetal intermediates

Gonçalves

Noseda

Duarte

et al. 2005

Carbohydrate Research

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Section: Resultssupporting

confidence: 63%

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl β-d-galactopyranoside and derivatives via dibutylstannylene acetal intermediates

Gonçalves

Noseda

Duarte

et al. 2005

Carbohydrate Research

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“…The stannanediyl acetal 21 [71] [75] of the 4,6-0 -benzylidene-a -D-mannopyranoside 20 [76] is selectively benzylated at HO-C(3) and benzoylated at HO-C(2) [71] [77]. Similarly, treatment of 21 with Et,N.…”

mentioning

confidence: 99%

Temporary Protection and Activation in the Regioselective Synthesis of Saccharide Sulfates

Langston

Bernet

Vasella

1994

Helvetica Chimica Acta

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Regioselective sulfation with Et,N. SO, of partially protected or unprotected glycosides via stanndnediyi acetals or stannyl ethers, combined with persistent or temporary protecting groups is described. Stannylation of phenylboronates, followed by sulfation and aqueous workup, is an efficient way for the synthesis of monosulfated monosaccharides. The stannanediyl acetal 2 led in high yields to 3a, while sulfation of the diol 1 proceeded more slowly and led in lower yield to a mixture 1/3a/4a/Sa (Scheme 1 ) . The trehalose disulfate 8a was obtained in high yields from 7; reducing the amount of sulfating agent led to a mixture 6/8a/9a. Stannylation and sulfation of the galactoside 11 afforded 13a, while direct sulfation of 11 gave a mixture of the 2-and 3-sulfates 13a/14a besides some disulfate 15a. Sulfation of the lactose derivative 16 and the stannanediyl acetal 17 gave the 3-sulfate 18a, with some disulfate 19a being formed from 16. The mannopyranoside 21 was selectively sulfated at OH-C(2), leading to 22a, while the corresponding diol 20 yielded mostly the isomer 23a and some disulfate 24a. Sulfation of the stannyl ethers derived from the gluco-and galactopyranosides 25 and 28 and ( B U , S~)~O afforded high yields of the 2,6-disulfate 26a and the 3,6-disulfate 29a, respectively. Stannylation of 25 and 28 with Bu2Sn0 and sulfation proceeded less satisfactorily. Stannylation of the phenylboronate 32 (Bu2SnO) and sulfation gave good yields of the 2-sulfate 27a; stannylation and benzoylation yielded the 2-benzoate 34 (Scheme 2). Similarly, the galactose-derived 37 provided high yields of the 3-sulfate 30a and of the 3-benzoate 39. Direct sulfation of the phenylboronates 32 and 37 proceeded in lower yields and gave mixtures.Introduction. -Sulfated saccharides and glycoconjugates occur extensively and are endowed with a number of important biological functions [l-231. In the preparation of defined carbohydrate sulfates, the sulfate group is, as a rule, introduced near the end of the synthesis to obviate the need of a sulfating agent which introduces the sulfate group in a protected form, such as the phenyl chlorosulfate described by Penney and Perlin [24]. Consequently, persistent protecting groups such as benzyl ethers have most often used in the synthesis of sulfated oligosaccharides [S] [25-311. The alcohol is usually treated directly with one of the most common sulfating reagents, complexes of SO, and a Lewis base such as DMF, pyridine, or a trialkylamine [32], although the SO,.DMF complex has also been used to form sulfates from nitrite esters [6] [33] or trimethylsilyl ethers [34] of cellulose. The sulfate group has also been introduced by displacing the triflate anion with tetrabutylammonium hydrogensulfate [35]'). The regioselective sulfation of partially protected glucose [44] or galactose [45] and some disaccharides [46] proceeds similarly to other 0 -acylations. Sulfation at the primary

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“…A mixture of two products were observed. The desired sulfate (85) was isolated in only a 49% yield the other half of the starting material had reacted to form the 6-methyl ether (86) (see This is another example of the potential for the trifluoroethyl group to act as a leaving group. From this reaction it maybe possible to derive some conclusions about the mechanism for the deprotection with methoxide.…”

Section: Deprotection Using Sodium Methoxidementioning

confidence: 99%

Development of a protecting group for sulfate esters

Proud

Prodger²,

Flitsch

1997

Tetrahedron Letters

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This work describes the development of a protecting group for sulfate monoesters in carbohydrates. After initial trial studies, the trifluoroethyl ester was selected as a suitable protecting group. The ester was formed from the sulfate by treatment with trifluorodiazoethane. This protection method is shown to be compatible with other common protecting groups used in carbohydrate chemistry. The protecting group is proven to be stable to the manipulations of many other protecting groups. The utility of monosaccharides incorporating protected sulfate esters in synthesis has been examined. It has been proven that they are useful and versatile building blocks in the synthesis of more complex structures. Selective cleavage of the trifluoroethyl ester was achieved with potassium tert-butoxide. The mechanism for this deprotection reaction has been studied and this investigation has led to the advancement of alternative deprotection methods.

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Organotin derivatives and the selective acylation and alkylation of the equatorial hydroxy group in a vicinal, equatorial-axial pair

Cited by 129 publications

References 9 publications

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl β-d-galactopyranoside and derivatives via dibutylstannylene acetal intermediates

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl β-d-galactopyranoside and derivatives via dibutylstannylene acetal intermediates

Temporary Protection and Activation in the Regioselective Synthesis of Saccharide Sulfates

Development of a protecting group for sulfate esters

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