Kishi s rule

The steric course of the osmylation of five higher sugar olefins, such as compounds 44 has been examined. Kishi s rule was I ound to be obeyed in all but one case (44, X,Y = O). ... 

In accordance with Kishi s rule osmylation of the carbohydrate derived unsatuiated ester (28) gave the D- and Lrthreo-D-gluco-configurated products (29) and (30) in the ratio 9 1 (Scheme 10), and similar selectivity was observed in the... 

In order to confirm that the stereoselectivity followed Kishi s empirical rule for dihydroxylations, the (Z)- and ( )-aUylic alcohols were prepared using (methoxy-carbonylmethylene)triphenylphosphorane 2 and formylmethylenetriphenylphos-phorane 3, respectively, followed by reduction with diisobutylaluminum hydride. The catalytic dihydroxylation in the presence of osmium tetroxide and N-methyl-morpholine N-oxide (NMO) afforded the D-glycero-isomer 6 from olefin 4 whereas the L-glycero-isomer 9 was obtained, as a major product, from the (F)-isomer 7. Finally, the separation by column chromatography or by protection/deprotection sequences provided the pure D-glycero-o-manno-heptose 10 and i-glycero-D-manno-heptose 11 (Scheme 2.3). 

One more side product was found, /ra s-diene 76. This compound runs immediately after 1 on HPLC and unfortunately co-crystallizes with discodermolide. It is apparently formed in small amounts during the acid cleavage of the silyl groups, although its formation as a consequence of the Nozaki-Hiyama-Kishi reaction cannot be ruled out. 

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