Ring Expansions of Cyclopropanated Carbohydrates

<p>The combination of cyclopropanes and carbohydrates functionality within a single molecule gives the synthetic chemist an interesting combination of reactivity and chirality to expand further upon. However, until recently relatively little work has been done in this field. Following the report of methodology to convert cyclopropanated carbohydrates into oxepines in high yields, this investigation set out to improve the selectivity of the rearrangement and also investigate the further utility of the subsequent products. Focused investigation of the starting substrates and reaction conditions led to a minor adaptation of the previously successful methodology for the ring expansion of cyclopropanated glycals. This resulted in a substantial increase in the selectivity of the reaction to generate oxepine rings in good to excellent yields with a range of nucleophiles. One of the oxepines was subsequently chosen for elaboration into a range of synthons for further investigations. These yielded a variety of oxepanes in good yields with well defined stereo- and regioselective outcomes. In the course of these reactions several unexpected products were isolated. These were further investigated with labelling experiments and a mechanism for their formation was proposed. Finally the methodology was applied to the total synthesis of a naturally occurring oxepine containing compound. Despite the apparent simplicity of the target, the effort was ultimately unsuccessful.</p>