New procedures for the Juliá–Colonna asymmetric epoxidation: synthesis of (+)-clausenamide

Biotransformations of 2,3-epoxy-3-arylpropanenitriles by Debaryomyces hansenii and Mortierella isabellina cells

“…The crude mixture was separated by column chromatography on silica gel with a hexane-ethyl acetate (3:1 v/v) mixture as the eluent, yielding the appropriate unreacted 2,3-dihydroxy-3-phenylpropanenitrile 4a and the mixture of two isomeric monoacetylated diols 7a and 8a as the products of kinetic resolution (see Table 4). 1 H and 13 C NMR spectra of enantiomerically enriched cyanohydrin (À)-4a were identical with those obtained by hydrolysis of trans1a. The spectra and elemental analyses of the obtained monoacetylated diols are reported below.…”

“…The enantiomeric excesses were determined by HPLC analysis using a Chiracel OD-H column (in n-hexane-i-propanol, 7/3 v/v for unreacted nitriles and 9/1 v/v for cyanohydrins, f = 0.6 mL/min). 1 13 …”

“…Optically active products of such biotransformations are important substrates in the preparation of several biologically active compounds. For example, oxiranecarboxamides and oxiranecarboxylic acid esters prepared from the corresponding oxiranenitriles are known as useful building blocks in the synthesis of (+)-clausenamide, 1 (+)-neoclausenamide, 2 (À)-dehydroclausenamide, 3 that is, compounds used in the synthesis of Taxol Ò . 4 The products of these biotransformations are also important and versatile intermediates in the synthesis of several pharmaceuticals such as the selective leukotriene antagonist SK&F 104353 5 or diltiazem, 4b,6 a potent coronary vasodilating agent.…”

Asymmetric Epoxidation in Stereoselective Synthesis

“…40 When 10 mol% of ketone 55 was used, high enantioselectivity (up to 95% ee) was achieved for the asymmetric epoxidation of trans-olefin 56 (Scheme 35.14). 41 Ketone 54 has been applied by scientists at Tanabe Seiyaku Company (Osaka, Japan) in the large-scale preparation of chiral epoxide 59 58 with ketone catalyst 54 and Oxone provided epoxide 59 in 87% yield and 79% ee. The epoxide was further purified by recrystallization to afford pure 59 in 64% yield and >99% ee.…”

“…[55][56][57] In 1980, Julia and co-workers 58 reported on the first highly enantioselective epoxidation (in >90% ee) of chalcones catalyzed by polyamino acids (Scheme 35.22). 59 Typically, the reaction was carried out under mild conditions in a triphasic system (toluene, water, and polymer catalyst) using hydrogen peroxide as an oxidant. A relatively large quantity of the polymer was required for the reaction (typically 0.4 g of polymer to 0.5 g of substrate), but the polymer could be recovered and reused after the application.…”