Glycosyl Imidates, 42 Selectively Protected Lactose and 2‐Azido Lactose, Building Blocks for Glycolipid Synthesis

Jung, Karl‐Heinz; Hoch, Monika; Schmidt, Richard R.

doi:10.1002/jlac.198919890276

Cited by 59 publications

(16 citation statements)

References 24 publications

(5 reference statements)

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“…of Et,N.SO, gave 51 % of a 4:1 mixture of the 3-and 2-sulfates 13a/14a and 10% of the 2,3-disulfate 15a. Sulfation of both the lactose derivative 16 [68] and the corresponding stannanediyl acetal 17 gave the 3-sulfate 18a as the sole monosulfated product in 77 and 83% yield, respectively. Sulfation of 16 occurred more slowly and also gave 11 YO of the disulfate 19a.…”

mentioning

confidence: 98%

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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mentioning

confidence: 98%

Temporary Protection and Activation in the Regioselective Synthesis of Saccharide Sulfates

Langston

Bernet

Vasella

1994

Helvetica Chimica Acta

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“…Chemoselective 1-O-deacetylation with hydrazinium acetate in DMF (Ǟ 2) and then reaction with trichloroacetonitrile in the presence of DBU as base afforded the desired trichloroacetimidate 3 as glucosyl donor. The glycosylation of known 6-O-, 3-O-, and 4-O-unprotected sugars 4a, [26] 4b, [27] and 4c [28] as acceptors ( Figure 1) with 3 as donor in the presence of TMSOTf as catalyst in dichloromethane led exclusively to β-linked glycosides 5a-c in satisfactory yields. Owing to the fluorescent properties of the products, monitoring of the reaction by TLC was convenient.…”

Section: Dpm Groupmentioning

confidence: 99%

“…Selective removal of the 1-O-acetyl group with hydrazinium acetate (Ǟ 11) and base-catalyzed reaction with trichloroacetonitrile led to trichloroacetimidate 12. Glycosylation of acceptors 4a-e [27][28][29]33] with 12 under standard conditions, that is, trimethylsilyl trifluoromethanesulfonate catalysis in dichloromethane, afforded the desired β-glycosides in almost quantitative yields (Scheme 4), thus illustrating the power of this glycosyl donor. However, unexpectedly, the cleavage of the DMG group turned out to be very difficult; neither hydrazine in ethanol nor base and ensuing acid treatment was successful.…”

Section: The Dmg Groupmentioning

confidence: 99%

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New Diacylamino Protecting Groups for Glucosamine

Aly

Schmidt

2005

Eur J Org Chem

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Glucosamine was transformed into N-diphenylmaleoyl (DPM), (DMG), and N-diglycolyl (DG) derivatives which furnished O-acetyl-protected O-glycosyl trichloroacetimidates 3, 12, and 20, respectively, as glycosyl donors. Their reactions with various acceptors 4 in the presence of TMSOTf as catalyst afforded the corresponding β-glycosides 5a-c, 13a-e, and 21a,d,f,g generally in high yields. Investigations into the cleavage of the N-protecting

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“…The organic layer was dried (MgSO,) and concentrated. The brown residue was purified by flash chromatography (petroleum ether/ethyl acetate = 8:2) to give 4.00 g (86%) sirup; 0-(2-azido-3,6-di-O-benzyl-2-deoxy-~-~-glucopyranosyl) -(1-3 j-0-(2,4,6-tvi-O-benzyl-~-~-galactopyranosyl) -(1-4) -0-(2-azido-3,6-di-O-benzyl-2-deoxy-~-~-gEucopyranoside j (14): A solution of the trichloroacetimidate 12 (200 mg, 0.20 mmol) and the acceptor substrate 13 (186 mg, 0.20 mmol) in the minimal amount of dichloromethane necessary for dissolution (ca. 3 ml) was cooled to -20°C under argon, and then n-hexane was added (8 ml).…”

Section: -0-(3-0-allyl-246-tri-o-benzyl-~-~-galactopyranosyl) -2-amentioning

confidence: 99%

Tumor‐associated antigen synthesis synthesis of the gal‐α‐(1→3)‐gal‐β‐(1→4)‐GlcNAc epitope a specific determinant for metastatic progression?

Schaubach¹,

Hemberger²,

Kinzy³

1991

Liebigs Ann. Chem.

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A versatile synthesis of the Gal-cl-(l-+3)-Gal-P-(1+4)-GlcNAc epitope coupled to an alkyl spacer molecule could be developed. The important building block 3'-allyl-~-lactal6 was prepared in high yield by the action of dibutyltin oxide and ally1 bromide on D-lactal and converted in several steps into the lactosamine derivative 13 with free 3'-OH group. Stereoselective glycosidation with the P-trichloroacetimidate of benzylated D-galactose 18 led to the trisaccharide in high yield. Activation of the protected Gal-a-( 1+3)-Gal-P-(1+4)-GlcNAc derivative 21 by desilylation and trichloroacetimidate formation followed by glycosidation with ethyl 9-hydroxynonanoate furnished the spacer-bound trisaccharide hapten 24 in excellent yield after simple two-step deprotection. The trisaccharide hapten 24 can easily be used as immunogen after coupling to an immunogenic carrier.The expression of Gala-( 1-+3)-Gal cell surface residues was correlated with the metastatic potential of malignant human cancer cells whereas benign breast biopsies and normal cells were Gal-a-(1+3)-Gal negative '). In contrast, man produces large amounts of a natural IgG antibody that interacts specifically with the Gal-a-(1-+3)-Gal-f3-(1+4)-GlcNAc r e~i d u e~,~) .This natural antibody, designated as "anti-Gal", constitutes approximately 1 % of circulating IgG in man4). It is argued5) that abnormal expression of the epitope on human glycoproteins may result in anti-Gal-mediated autoimmune processes.For the evaluation of monoclonal antibodies as well as for the stimulation of human immune response against the Gal-a-(l-+3)-Gal-P-(1+4)-GlcNAc epitope it was necessaryto develop a short and efficient synthesis of the proposed structure.The synthesis of an analogous compound described recently by Garegg et al.6) was achieved by a multistep synthesis (23 steps) whereas in the present approach the compound was prepared straightforwardly in 15 steps. The method of glycosylation used here is based on the versatile trichloroacetimidates introduced by Schmidt and coworkers ' ).For strategic reasons the use of D-lactal as a precursor for D-lactosamine was desirable to minimize the crucial glycosylation steps. So, first the synthesis of a 3-0-unprotected derivative of lactosamine was achieved by the following strategy: The readily available D-laCtal 1 could be converted by the well-known dibutyltin oxide alkylation procedure') into the monobenzylated or monoallylated derivatives 2 and 6. As byproducts the di-0-alkylated derivatives 4 and 7 could also be isolated in small amounts.The sites of alkylation of 2 (TAC = trichloroacetylcarbamoyl) were assigned by 0-carbamoylation lo) with tri-1

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Glycosyl Imidates, 42 Selectively Protected Lactose and 2‐Azido Lactose, Building Blocks for Glycolipid Synthesis

Cited by 59 publications

References 24 publications

Temporary Protection and Activation in the Regioselective Synthesis of Saccharide Sulfates

Temporary Protection and Activation in the Regioselective Synthesis of Saccharide Sulfates

New Diacylamino Protecting Groups for Glucosamine

Tumor‐associated antigen synthesis synthesis of the gal‐α‐(1→3)‐gal‐β‐(1→4)‐GlcNAc epitope a specific determinant for metastatic progression?

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