Arabinose-derived ulose

Shing and coworkers reported arabinose-derived uloses (59, 60) as epoxidation catalysts, and phenyl stilbene can be epoxidized by 60 in up to 90% ee (Fig. 20) [113-115]. In 2003, Zhao and coworkers reported aldehyde 61 to epoxidize trans-stilbene in up to 94% ee [116]. 

CATALYTIC ENANTIOSELECTIVE EPOXIDATION OF TRANS-DISUBSTITUTED AND TRISUBSTITUTED ALKENES WITH ARABINOSE-DERIVED ULOSE... 

We recently reported our results on the asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes, using Oxone as oxidant, catalyzed by readily available arabinose-derived 4-uloses containing tunable steric blockers that control the enantioselectivity of the epoxidation.Ulose (3), containing a 2, 3 -diisobutyl acetal unit, was the most efficient catalyst and displayed good enantioselectivity. 

In the presence of molecular oxygen, D-arabinose (82) is the major deamination product. D-tfrafeino-Hexos-2-ulose (79) is also formed, but the formation of 2-deoxy-D-hexonic acid (80) and 2-deoxy-D-ert/fhro-hexos-3-ulose (81) is suppressed. It has been suggested34 that the peroxyl radical derived from the W-centered radicals (78) may be, in part, the precursor of D-arabinose. A mechanism similar to the... 

Shing et al. have prepared a number of arabinose (commercially available in both enantiomeric forms) derived 4-uloses and examined their potential as chiral dioxirane precursors. The most successful of these ketones was found to epoxidize phenylcyclohexene in 92% yield and 85% ee (Scheme 24) <2003TL9225>. 

Oxidative unmasking, enantiospecific reduction" of the enone (55), and stereoselective cix-hydroxylation on the allylic acetates (56a and 56b) paved the way for the first report on the synthesis of the spiro-C-linked disaccharides (57a and 57b). Extension of the same strategy to the uloses derived from d- and L-arabinose expectedly offered the enantiomeric spiro-C-linked disaccharides (58a and 58b and 59a and 59b, respectively Scheme 22.13). 

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