✍ Scribed by Priv.-Doz. Dr. Carsten Strohmann; Dipl.-Chem. Bors Cajus Abele
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anti-16 product can be used as an example to demonstrate the differentiation between the double bonds in the corresponding metathesis product. Careful ozonolysis of anri-16 monitored by thin-layer chromatography, followed by reductive workup with lithium aluminum hydride, yielded 79 % of the monoprotected aminodiol 17, which offers a variety of possibilities for further elaboration
Typical procedure for the stereoselective ring-closing metathesis as exemplified by ent-sv-16 (Table 1, entry 11): ent-12 (SO mg, 0.13 mmol) was dissolved in anhydrous benzene (9.2 mL) under argon, [Mo] (4.9 pmol, 5 mol%) was then added, and the resulting mixture was stirred for 3 d at a bath temperature of 80°C. The solvent was removed and the residue was purified by flash chromatography on silica gel by using iert-butyl methyl ether/petroleum ether (1 :40) as eluent to afford 44 mg (97 %)of the cyclization product (72 % de, GC) as a yellow oil. Selected spectroscopic data: 'H NMR (400 MHz, CDCI,). two amide isomers, combined spectrum:
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