Synthesis of L-Pyranosides from 5-Enopyranosides by Diastereoselective Hydroboration/Oxidation. -The reaction provides a simple and efficient approach to L-idoside and L-glucoside as well as to L-iduronic acid (IV). Interestingly, in the case of 5-enoglucosides the diastereoselective outcome is strongly dependent on the amount of BH3. -(TAKAHASHI, H.; MIYAMA, N.; MITSUZUKA, H.; IKEGAMI*, S.; Synthesis 2004, 18, 2991-2994; Fac. Pharm. Sci., Teikyo Univ., Sagamiko, Kanagawa 199-01, Japan; Eng.) -Jannicke 21-204

Unusual sugar dimers: The synthesis of 6,6′‐ether‐connected pyranoses by an acetalization–reduction procedure is described (see scheme). Structure–activity‐relationship studies of these novel carbohydrate dimers suggested that the natural product coyolosa, which has been shown to have a significant effect on fasting blood‐glucose levels, may have a different structure from the one previously reported.

Improved synthesis of L-pyranosides utilizing diastereoselective hydroboration/oxidation of 5-enopyranosides was investigated. A unique phenomenon in the diastereoselectivity of the hydroboration was incidentally found. The method was successfully applied to the synthesis of L-iduronic acid.

Development of a Novel Sugar Linkage: 6,6'-Ether-Connected Sugars. -6,6'-Ether-connected pyranoses are prepared by a new acetalization-reduction procedure which can also be performed as a one-pot procedure. In both cases the reaction occurs in the presence of Tms-O-Tf. The method is applicable to D-gluco, D-galacto, D-manno-and D-allo-pyranosides with a variety of aldehyde derivatives. For an efficient one-pot reaction the 6-O-Tms-derivatives ar used as the starting material. -(TAKAHASHI, H.; FUKUDA, T.; MITSUZUKA, H.; NAMME, R.; MIYAMOTO, H.; OHKURA, Y.; IKEGAMI*, S.; Angew. Chem., Int. Ed. 42 (2003) 41, 5069-5071; Fac. Pharm. Sci., Teikyo Univ., Sagamiko, Kanagawa 199-01, Japan; Eng.) -Adam 07-182

Ungewöhnliche Zuckerdimere – 6,6′‐Ether‐verknüpfte Pyranosen – werden durch Acetalbildung und Reduktion im Eintopfverfahren erhalten (siehe Schema). Untersuchungen zu Struktur‐Wirkungs‐Beziehungen dieser Verbindungen legen nahe, dass der aus Acrocomia mexicana isolierte, hypoglycämisch wirkende Naturstoff Coyolosa eine andere Struktur hat, als bisher vermutet.