Glycosyl Imidates, 66. Synthesis of the Tetrasaccharide Moiety of Plant Growth Regulator Calonyctin A

✍ Scribed by Jiang, Zi-Hua ;Schmidt, Richard R.

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 735 KB
• Volume: 1994
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199419940702

✦ Synopsis

Abstract

3‐O‐Benzyl‐protected quinovose 6 was transformed into 1,2‐O‐unprotected derivative 9 which on treatment with TBS‐Cl in the presence of a base gave selectively 2‐O‐unprotected glycosyl acceptor 10. Similarly, 3‐O‐allyl‐protected quinovose 11 was transformed into 1,2‐O‐unprotected derivative 14. 1,2‐O‐Acetylation of 14, selective removal of the 1‐O‐acetyl group with hydrazinium acetate, and subsequent treatment with trichloroacetonitrile in the presence of DBU furnished the versatile 2‐O‐acetyl‐3‐O‐allyl‐protected quinovosyl donor 17. Reaction of donor 17 with acceptor 10 in the presence of TMSOTf as the catalyst gave disaccharide 19. Treatment of 19 with NaOMe/MeOH provided 2b‐O‐unprotected derivative 20 which gave with rhamnosyl donor 18 in the presence of TMSOTf as the catalyst trisaccharide 21. 3b‐O‐Deallylation of 21 and subsequent reaction with donor 17, again in the presence of TMSOTf as the catalyst, gave target tetrasaccharide 2. Removal of all O‐protective groups furnished D‐Quiß(1→3)[L‐Rhaα(1→2)]D‐Quiß(1→2)D‐Qui (3), the tetrasaccharide moiety of calonyctin A. magnified image