Synthesis of 5 thioDglucose acetone pyridine water pyridine

Synthesis of 5 -thio-D-glucose acetone pyridine water pyridine NH 3 (liq. )

Synthesis of 5 -thio-D-glucose

Synthesis of 5 -thio-D-glucose 5 -thio-D-glucopyranose

Synthesis of 5 -thio-D-glucose (2) D-glucose acetone water pyridine

Synthesis of 5 -thio-D-glucose (2)

Synthesis of 5 -thio-D-glucose (2) 5 -thio-D-glucopyranose

Generation of epoxide rings

Generation of epoxide rings This reaction is thought to occur via 3 S conformation in which the 5 substituents at C-2 and C-3 adopt required trans-diaxial orientation (because of the SN 2 mechanism). In the former case (previous slide) the rigidity imposed by the 1, 6 -anhydro ring (fusion of two rings through two bonds) prevents the assumption of a related conformation.

Opening of epoxide rings

Opening of epoxide rings

Opening of epoxide rings

Opening of epoxide rings major product minor produc

Opening of epoxide rings • When the epoxide rings are fused in conformationally restricted derivatives such as 1, 6 -anhydropyranoses or transfused 4, 6 -O-benzylidenehexopyranosides, pyranoid rings adopt half-chair conformations, and the diastereoisomers having diaxial arrangement at the epoxide ring opened positions represents more than 90 % of the products of the nucleophilic opening of the epoxide ring. • This is in accordance with the Fürst-Plattner rule, formulated from studies of the nucleophilic opening of steroidal epoxides, which can be explained by consideration of the transition states in the ring opening reactions.

Opening of epoxide rings A A A major product minor product Accessibility of the nucleophile for opening of epoxide rings fused with a sixmembered ring is due to the SN 2 geometry of the intermediate better for generation of an axial bond (route a) than for generation of an equatorial bond (route b).