1,2-Diols, periodate oxidative degradation

Periodate oxidation of the cw-diol in lythrancine 101 and Hofmann degradation of lythrancine 101,102, and 103 were tried but all attempts were unsuccessful (55). 

The methods for oxidation of sugars discussed so far leave the basic skeleton intact. A reagent that leads to C-C bond rupture is periodic acid, HIO4. This compound oxidatively degrades vicinal diols to give carbonyl compounds. 

Hofmann degradation of the nonnatural protoberberine 454 afforded the 10-membered ring base 455 (65%) in addition to the styrene-type compound (13%) (Scheme 92). Dihydroxylation of the former with N-bromosuccinimide in the presence of a large excess of hydrochloric acid and subsequent oxidation of the product diol 456 with periodic acid afforded the dialdehyde 457. On irradiation in tert-butyl alcohol 457 provided ( )-cis-alpinigenine (445) along with ( )-alpinigenine (441) as a result of endo and exo intramolecular cycloaddition, respectively, of the intermediate photodienol (221,222). 

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