Stereoselective Synthesis of β-D-Mannopyranosides with Reactive Mannopyranosyl Donors Possessing a Neighboring Electron-Withdrawing Group

✍ Scribed by Adel A.-H. Abdel-Rahman; Simon Jonke; El Sayed H. El Ashry; Richard R. Schmidt

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 84 KB
• Volume: 41
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/1521-3773(20020816)41:16<2972::aid-anie2972>3.0.co;2-4

✦ Synopsis

Scheme 1. Preferred a-and b-mannopyranoside synthesis. Scheme 2. Mechanistic proposals for preferred b-mannopyranoside formation. TB ¼ Twist± Boat conformation, H ¼ half-chair conformation. 2973 Scheme 3. Synthesis of 4 from 1; a) BnSO 2 Cl, pyr (91 %); b) CAN, MeCN/H 2 O (4:1), O 8C (82 %); c) CCl 3 CN, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (94 %); d) TMSOTf, CH 2 Cl 2 , À50 8C (80 % b:a ¼ 8:1); e) NaNH 2 , DMF, RT (91 %). All ¼ allyl; MPM ¼ paramethoxybenzyl. Scheme 4. Synthesis of Manb(1-4)GlcNAc disaccharide from 6 and 8 (R ¼ Bn); a) TDS-Cl, imidazole, DMF (95 %); b) BnSO 2 Cl, pyr (92 %); c) TBAF, THF (90 %); d) CCl 3 CN, DBU, CH 2 Cl 2 (97 %); e) TMSOTf, CH 2 Cl 2 (82 %; b:a ¼ 9:1); f) TMSOTf, CH 2 Cl 2 (78 %, b:a ¼ 7.4:1); g) NaNH 2 , DMF, RT (93 %).

advantageous selective access to the 2-hydroxy group of the mannose residue is provided.