Abstract
Synthesis of 1,6-anhydro sugars is well known in literature. The dioxolane ring exhibits at least two types of properties. It can be used as a protecting group and reaction site. This work discusses the cleavage of the 1,6-anhydro ring of muramic acid derivatives. To induce the opening of the dioxolane ring in 1,6-anhydro-D-glucose derivatives three types of reagents were used (TFA/Ac2O, Sc(OTf)3/Ac2O, H2SO4/Ac2O). This method is commonly used in sugar chemistry for opening 1,6-anhydro ring. This process led to the preparation of compounds with very good yields (80%, even 98%).
In the first attempt the mixture of TFA/Ac2O (1:9) was used. Besides the main product 4, the 3,4-di-Oacetyl- 1,6-anhydro-2-azide-2-deoxy-β-D-glucopyranose was observed as a side product. Main product 4 was obtained as the mixture of α and β (2:1) anomers. Better stereoselectivity was obtained using Sc(OTf)3. In this case, the main product was received with β configuration. The best yield (65%) was obtained using a mixture of H2SO4 and Ac2O and mixture of two anomers of N-acetyl-1,4,6-tri-Oacetyl- 2-deoxy-D-muramic acid ethyl ester was isolated (α and β, 1:4).
Depending on which method was used to open dioxolane ring of 1,6-anhydroMur derivative we were able to control the stereochemistry of the reaction and to obtain pure α anomer or mostly β anomer.
Keywords: Mur-derivative, 1, 6-anhydro derivative, cleavage of 1, 6-anhydro linkage, dioxolane ring, TFA/Ac2O, Sc(OTf)3/ Ac2O, H2SO4/Ac2O.
Graphical Abstract
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