Loganin aglycone synthesis

Sultam-modified acrylates undergo [4 + 2]-cy-cloadditions with 1,3-dienes with excellent endo- and side-selectivity in the presence of EtAlCl2 or TiCl4 [7-9]. This feature could be used for an effective synthesis of the loganin-aglycon 9 (Scheme 2) [10] ... 

Activattd dimethyl sulfoxide oxidations have been fairly well used in the synthesis of monoterpenes, as seen in the oxidation to an aldehyde of the alcohols (40), en route to loganin aglycone, and (41), a precursor in a synthesis of specionin (equation 16). ... 

The appreciable synthetic potential of the de Mayo reaction has been applied to the preparation of polycyclic natural products. Some recent developments are shown in Table 4. The de Mayo reaction was used as the key step in the synthesis of hirsutene (entry 1), fusicoccin H aglycone (entry 2), taxanes (entries 3 and 4), loganin (entries 8 and 9), sarracenin (entry 10) and iridoid intermediates (entry 11). 

Oppolzer et al. developed useful auxiliaries based on a camphor precursor,231 and one of the best was a sultam (277). When this sultam was converted to an acrylamide (278) and reacted with butadiene, cycloadduct 280 was produced (85% yield, 95 % ee).232 Selectivity in this Diels-Alder reaction is due to chelation of the amide oxygen and the sulfonyl group, as shown in 279. Oppolzer and co-workers applied this methodology to a chiral synthesis of the aglycone of loganin.233... 

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