Satoru Masamune

Horner-wadsworth-emmons reaction: Use of lithium chloride and an amine for base-sensitive compounds

Abstract A mild olefination procedure, utilizing LiCl and an amine, has been developed for use with base-sensitive aldehydes and phosphonates.

Asymmetric catalytic cyclopropanation of olefins : bis-oxazoline copper complexes

Abstract Bis-oxazolines (1–7) prepared from diethyl malonate and chiral amino alcohols were converted into their Cu(II) complexes which, upon activation, exhibit high enantioselectivity of up to 99 %ee for catalytic cyclopropanation of olefins.

Asymmetric copper-catalyzed cyclopropanation of trisubstituted and unsymmetrical cis-1,2-disubstituted olefins: modified bis-oxazoline ligands

Abstract The Cu(I) complexes of new bis-oxazolines (3–7) prepared from the corresponding amino alcohols and malono-bis-imidate exhibit high enantioselectivity of up to 94 %ee in the catalytic cyclopropanation of trisubstituted and unsymmetrical cis-1,2-disubstituted olefins. New diazoacetate reagents have also been developed giving high trans/cis ratios of up to 99:1 trans.

Total synthesis of the L-hexoses

Enantiomerically pure polyhydroxylated natural products are synthesized by using a reiterative two-carbon extension cycle consisting of four steps. The generality and efficiency of this methodology are demonstrated in the total synthesis of all eight L-hexoses.

An improved, convenient procedure for reduction of amino acids to aminoalcohols : use of NaBH4-H2SO4

Abstract The use of NaBH4-H2SO4, For the reduction of α-amino acids to the corresponding aminoalcohols offers definite advantages: i) operational simplicity, ii) ease of scaling up the reaction without risking explosion, and iii) use of the inexpensive reagents.

Degradation of poly(3-hydroxybutyrate) by poly(3-hydroxybutyrate) depolymerase from Alcaligenes faecalis T1

The extracellular poly(3-hydroxybutyrate) depolymerase purified from Alcaligenes faecalis T1 has two disulfide bonds, one of which appears to be necessary for the full enzyme activity. This depolymerase hydrolyzed not only hydrophobic poly(3-hydroxybutyrate) but also water-soluble trimer and larger oligomers of D-(-)-3-hydroxybutyrate, regardless of their solubilities in water. Kinetic analyses with oligomers of various sizes indicated that the substrate cleaving site of the enzyme consisted of four subsites with individual affinities for monomer units of the substrate. Analyses of the hydrolytic products of oligomers, which had labeled D-(-)-3-hydroxybutyrate at the hydroxy terminus, showed that the enzyme cleaved only the second ester linkage from the hydroxy terminus of the trimer and tetramer, and acted as an endo-type hydrolase toward the pentamer and higher oligomers. The enzyme appeared to have a hydrophobic site which interacted with poly(3-hydroxybutyrate) and determined the affinity of the enzyme toward the hydrophobic substrate.

KMnO4 revisited: Oxidation of aldehydes to carboxylic acids in the tert-butyl alcohol - aqueous NaH2PO4 system

Abstract Aldehydic compounds with one or more protected hydroxyl groups are effectively oxidized with KMnO4 to the corresponding carboxylic acids using a mixture of t -BuOH and aqueous NaH2PO4 as a reaction medium.

Synthesis and characterization of tetrakis(2,6-diethylphenyl)digermene

Tetrakis(2,6-diethylphenyl)digermene (1b) has been synthesized and its molecular structure determined: (1) the GeGe bond length is 2.213(2) A and (2) the molecule has a twist angle of 11° about the GeGe bond and an out-of-plane bending angle of 15° at the germanium atoms.

The catalytic asymmetric aldol reaction of aldehydes with unsubstituted and monosubstituted silyl ketene acetals: formation of anti-β-hydroxy-α-methyl esters

Abstract The title reaction with unsubstituted and monosubstituted silyl ketene acetals proceeds with high enantioselectivity, and in the latter case good diastereoselectivity favoring the anti-β-hydroxy-α-methyl esters in all reported cases.

Synthesis of amphotericin B. 2. fragment C-D of the aglycone

Abstract Fragment C-D, the C(21)-C(37) unit of the aglycone of amphotericin B, has been synthesized.