Preparation of acylated pyranoid glycals in neutral aqueous medium by using chromium(II) complexes as reagents

✍ Scribed by Gyöngyvér Kovács; Krisztina Tóth; Zoltán Dinya; László Somsák; Károly Micskei

• Book ID: 104209321
• Publisher: Elsevier Science
• Year: 1999
• Tongue: French
• Weight: 717 KB
• Volume: 55
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(99)00170-2

✦ Synopsis

Reactions of 2,3,4,6-tetra-O-acetyl-ct-D-glucopyranosyl bromide (3) with chromium(II)L complexes (L = EDTA, NTA` IDA, GLY, MAL) in neutral (5 < pH < 7) aqueous DMF gave 3,4,6-tri-O-acetyl-l,5anhydro-2-deoxy-D-arabino-hex-l-elfitol (13) in 70-90% yields and >95% purity. Complexes of Cr(lI) with L = EDTA, NTA were similarly efficient with 2,3,4,6-tetra-O-acetyl-ct-D-glucopyranosyl chloride (2) in furnishing glucal 13, while with L = IDA, GLY, MAL hydrolysis of 2 could not be suppressed. Under the same conditions [Cra(EDTA)] 2" also efficiently gave the corresponding glycals 14-19 from 2,3,4,6-tetra-O-benzoyl-(4) and 2,3,4,6-tetra-O-pivaloyl-ct-D-glucopyranosyl bromide (5), per-O-acetylated ct-D-galactopyranosyl chloride (6) and bromide (7), Ot-D-mannopyranosyl chloride ($), ct-D-xylopyranosyl chloride (9), and bromide (10), 13-Darabinopyranosyl bromide (11), and ot-L-rhanmopyranosyl chloride (12).