Total Synthesis of Zizyphin A and N-Acetylzizyphin B

✍ Scribed by Prof. Dr. Ulrich Schmidt; Dr. Albrecht Lieberknecht; Dipl.-Chem. Hilmar Bökens; Helmut Griesser

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 251 KB
• Volume: 20
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.198110261

✦ Synopsis

tols (12) or as lactol ethers (13). After protection of the hydroxy group in (9), deblocking leads to preparatively useful homoaldol derivatives with free carbonyl groups. Thus, the acetate of (9b) gives the y-acetoxyketone (14) in 94% yield.

Procedure (9): All operations must be carried out under N2 with rigorous exclusion of moisture. A 1 . 6 0 ~ solution of butyllithium (3.40 mL, 5.50 mmol) in hexane is transferred within 15 min at -78°C through a syringe cooled with dry-ice into a solution of (6)l7] (5.00 mmol) and TMEDA (0.83 mL, 5.50 mmol) in diethyl ether (15 mL). After 0.25-5 h (Table I), a solution of (8) (5.30 mmol, 1.06 equiv.) in a few mL of ether is added to the mixture at -78 to -70°C; after 2 hours stirring at this temperature the mixture is neutralized with glacial acetic acid (0.90 g, 15 mmol), allowed to warm, and worked-up in the usual way with etherlwater. Chromatography on ca. 60 g silica gel with ether/petroleum ether (1 : 1) furnishes pure (9). Rf=0.1-0.3 [(lo): R = 0.3 -0.51.