Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids.
Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids.
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DOI：
10.1021/acs.joc.6b02221
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发表时间：
2016-11-18
影响因子：
3.6
通讯作者：
Crich, David
中科院分区：
文献类型：
--
作者：
Dhakal, Bibek;Buda, Szymon;Crich, David
为了最终合成用于假氨基酸糖苷的立体控制合成的糖基供体，描述了在5位携带轴向叠氮化物的d-甘油-d-古洛唾液酸金刚烷基硫代糖苷的立体控制合成。该合成采用乙酰丙酸作为N-乙酰神经氨酸硫代糖苷氧化脱氨基的亲核试剂，导致形成选择性保护为5-O-乙酰丙酸的3-脱氧-d-甘油基-d-半乳糖基-2-壬酮糖酸（KDN）衍生物。用三氟甲磺酸酯代替乙酰丙酸酯能够引入轴向叠氮化物，从而形成糖基供体。当直接获得5-O-三氟甲磺酰基KDN衍生物时，较短的合成在氧化脱氨基步骤中使用三氟甲磺酸酯作为亲核试剂。在−78 °C下，用5-叠氮基-d-甘油基-d-古洛构型的唾液酰基金刚烷硫代糖苷进行的糖基化反应对于赤道糖苷的形成具有选择性，这表明当合适的供体变得可用时，赤道假氨基酸糖苷的合成将是可能的。一个相当的N-乙酰神经氨酸金刚烷硫代糖苷携带赤道叠氮化物在5-位置也被发现是选择性的赤道糖苷形成在相同的条件下，这表明重新调查其他叠氮化物保护NeuAc捐助者是值得的。在D-甘油-D-古洛系列中的糖基化立体选择性是根据供体的侧链构象来讨论的。
With a view to the eventual synthesis of glycosyl donors for the stereocontrolled synthesis of pseudaminic acid glycosides, the stereocontrolled synthesis of a d-glycero-d-gulo sialic acid adamantanylthioglycoside carrying an axial azide at the 5-position is described. The synthesis employs levulinic acid as nucleophile in the oxidative deamination of an N-acetyl neuraminic acid thioglycoside leading to the formation of a 3-deoxy-d-glycero-d-galacto-2-nonulosonic acid (KDN) derivative selectively protected as 5-O-levulinate. Replacement of the levulinate by triflate enables introduction of the axial azide and hence formation of the glycosyl donor. A shorter synthesis uses trifluoromethanesulfonate as nucleophile in the oxidative deamination step when the 5-O-triflyl KDN derivative is obtained directly. Glycosylation reactions conducted with the 5-azido-d-glycero-d-gulo configured sialyl adamantanylthioglycoside at −78 °C are selective for the formation of the equatorial glycosides suggesting that the synthesis of equatorial pseudaminic acid glycosides will be possible as suitable donors become available. A comparable N-acetylneuraminic acid adamantanylthioglycoside carrying an equatorial azide at the 5-position was also found to be selective for equatorial glycoside formation under the same conditions, suggesting that reinvestigation of other azide-protected NeuAc donors is merited. Glycosylation stereoselectivity in the d-glycero-d-gulo series is discussed in terms of the side chain conformation of the donor.
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影响因子：
1.8
作者：
Farris, Michael D.;De Meo, Cristina
通讯作者：
De Meo, Cristina
影响因子：
3.1
作者：
Bohe, Luis;Crich, David
通讯作者：
Crich, David
影响因子：
16.6
作者：
Balmond, Edward I.;Benito-Alifonso, David;Coe, Diane M.;Alder, Roger W.;McGarrigle, Eoghan M.;Galan, M. Carmen
通讯作者：
Galan, M. Carmen
影响因子：
2.8
作者：
Bülow, A;Meyer, T;Bols, M
通讯作者：
Bols, M
影响因子：
2.8
作者：
Attolino, Emanuele;Catelani, Giorgio;D'Andrea, Felicia
通讯作者：
D'Andrea, Felicia