Deacetalisation-bicyclisation routes to novel polycyclic heterocycles using stannous chloride dihydrate

The stannous chloride dihydrate-mediated deprotection-bicyclisation of a range of amides possessing a pendant acetal group is reported. These mild reaction conditions have been used to prepare a number of ring-fused heterocyclic compounds, some in enantiomerically pure form, which should be of interest both in their own right and as building blocks for the production of more complex target molecules.     

Novel bicyclisation of unsaturated polyols in PdCl2-CuCl2-AcOH catalytic system

Novel type of Pd(II)-catalysed transformation of sugar-derived alkenitols furnishing 7-benzyloxy-2,5-dioxabicyclo[2.2.1]heptanes was discovered. The investigated bicyclisation displays an exceptional substrate selectivity towards xylo-configured unsaturated polyols. Moreover, a newly build stereogenic centre is formed in a diastereospecific cis-manner. The observed stereochemical preference was corroborated by modelling of pertinent transition states at the semiempirical level of theory (PM5). In addition, the single crystal X-ray analysis of an acylated analogue d-glycero-l-gulo-21 was done in order to establish the relative configuration of related bicyclic products.