Preparation of optically-active 3-pyrrolidinol and its derivatives from 1-benzoylpyrrolidinol by hydroxylation with Aspergillus sp. and stereo-selective esterification by a commercial lipase.

An effective preparation scheme for optically-active 3-pyrrolidinol and its derivatives based on biological transformation is proposed. Aspergillus sp. NBRC 109513 hydroxylated 1-benzoylpyrrolidine, yielding (S)-1-benzoyl-3-pyrrolidinol with 66 % ee.

Amide-transforming activity of Streptomyces: possible application to the formation of hydroxy amides and aminoalcohols.

To develop an efficient bioconversion process for amides, we screened our collection of Streptomyces strains, mostly obtained from soil, for effective transformers. Five strains, including the SY007 (NBRC 109343) and SY435 (NBRC 109344) of Streptomyces sp., exhibited marked conversion activities from the approximately 700 strains analyzed.

Oxo-tethered ruthenium(II) complex as a bifunctional catalyst for asymmetric transfer hydrogenation and H2 hydrogenation.

Newly developed oxo-tethered Ru amido complexes (R,R)-1 and their HCl adducts (R,R)-2 exhibited excellent catalytic performance for both asymmetric transfer hydrogenation and the hydrogenation of ketonic substrates under neutral conditions without any cocatalysts to give chiral secondary alcohols with high levels of enantioselectivity.

Chiral ruthenabicyclic complexes: precatalysts for rapid, enantioselective, and wide-scope hydrogenation of ketones.

A novel ruthenabicyclic complex with base shows excellent catalytic activity in the asymmetric hydrogenation of ketones. The turnover frequency of the hydrogenation of acetophenone reaches about 35,000 min(-1) in the best case, affording 1-phenylethanol in >99% ee. Several aliphatic and base-labile ketones are smoothly converted to the corresponding alcohols in high enantioselectivity.

Direct asymmetric reductive amination.

Asymmetric reductive amination of beta-keto amides catalyzed by the chiral catalyst Ru(OAc)(2)((R)-dm-segphos) produces unprotected beta-amino amides with high yields and high enantioselectivities (94.7-99.5% ee).

Highly Enantio- and s-trans C=C bond selective catalytic hydrogenation of cyclic enones: alternative synthesis of (-)-menthol.

A highly enantioselective catalytic hydrogenation of cyclic enones was achieved by using the combination of a cationic Rh(I) complex, (S)-5,5'-bis{di(3,5-di-tert-butyl-4-methoxyphenylphosphino)}-4,4'-bi-1,3-benzodioxole (DTBM-SEGPHOS), and (CH2CH2PPh3Br)2. The presence of an s-cis C=C bond isopropylidene moiety on the cyclic enone influenced the enantioselectivity of the hydrogenation. Thus, the hydrogenation of 3-alkyl-6-isopropylidene-2-cyclohexen-1-one, which contains both s-cis and s-trans enones, proceeded in excellent enantioselectivity (up to 98 % ee).

Developments in asymmetric hydrogenation from an industrial perspective.

Examples of developments in asymmetric hydrogenation from various perspectives, in an effort to improve efficiency, are reported. Discussed in this Account are (1) the improved synthesis of BINAP ligands, (2) the design of SEGPHOS ligands for higher enantioselectivity, (3) a new protocol with fewer reaction steps to synthesize beta-aminoesters, and (4) a novel asymmetric hydrogenation mediated by a copper catalyst.

Asymmetric hydrogenation of aryl ketones mediated by a copper catalyst.

[reaction: see text] A novel asymmetric hydrogenation protocol using a copper catalyst is reported. A Cu(I) complex in the presence of nonracemic BDPP hydrogenates aryl ketones with moderate to high enantioselectivity.