Strychnos 1990 - 2004 - Crops for the Future
Strychnos 1990 - 2004 - Crops for the Future
Strychnos 1990 - 2004 - Crops for the Future
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Author<br />
Title<br />
Year<br />
Source title<br />
Reference<br />
Xu, Y., K. Ohori, T. Ohshima and M. Shibasaki<br />
A practical large-scale syn<strong>the</strong>sis of enantiomerically pure 3-[bis(methoxycarbonyl<br />
2002<br />
Tetrahedron<br />
58(13): 2585-2588<br />
Abstract<br />
A highly practical and efficient procedure <strong>for</strong> <strong>the</strong> large-scale (up to 6 mol) syn<strong>the</strong>sis of<br />
enantiomerically pure (R)-3-[bis(methoxycarbonyl)methyl]cyclohexanone using an (R)-<br />
AlLibis(binaphthoxide) complex ((R)-ALB)-catalyzed asymmetric Michael reaction was developed.<br />
The reaction was successfully accelerated under highly concentrated conditions without lowering<br />
chemical yield or <strong>the</strong> high enantiomeric excess. Under <strong>the</strong>se conditions, only 0.05 mol% of <strong>the</strong><br />
catalyst <strong>for</strong>ced <strong>the</strong> reaction to completion in 48 h. The work-up procedure was also improved and <strong>the</strong><br />
enantiomerically pure compound was obtained as a white crystal in up to 95% yield without<br />
chromatographic separation. Finally, pre-manufacturing scale syn<strong>the</strong>sis was per<strong>for</strong>med. Using 0.1<br />
mol% of <strong>the</strong> catalyst with 0.09 mol% of KO-t-Bu and MS 4 Angstrom, <strong>the</strong> Michael reaction of 2-<br />
cyclohexenone (6.0 mol, 581 mL) with dimethyl malonate (6.0 mol, 686 mL) was completed in 24 h<br />
at ambient temperature to af<strong>for</strong>d more than a kilogram of <strong>the</strong> enantiomerically pure product in 91%<br />
yield after three successive crystallizations. The described method renders <strong>the</strong> enantiomerically pure<br />
Michael adduct readily available on greater than kilo scale. (C) 2002 Elsevier Science Ltd. All rights<br />
r e s e r v e d .<br />
Author<br />
Title<br />
Year<br />
Source title<br />
Reference<br />
Zhao, S., X. B. Liao and J. M. Cook<br />
Enantiospecific, stereospecific total syn<strong>the</strong>sis of (+)-majvinine, (+)-10-methoxyaff<br />
2002<br />
Organic Letters<br />
4(5): 687-690<br />
Abstract<br />
[GRAPHICS] - The enantiospecific stereospecific total syn<strong>the</strong>sis of majvinine la, 10-<br />
methoxyaffinisine 1b, and N-a-methylsarpagine 1c are reported; this method has also resulted in <strong>the</strong><br />
total syn<strong>the</strong>sis of <strong>the</strong> Alstonia bisindole macralstonidine 2.