Maria Chrzanowska

Transformation of (+)-thiomicamine into a new ligand for the enantioselective addition of methyllithium to prochiral imines

Abstract A new ligand 2 was prepared from (+)-thiomicamine 1 and o-methoxyphenol, and its activity as an external controller of stereochemistry in enantioselective additions of methyllithium to prochiral imines 8–10 tested. The non-racemic secondary amines 11–13 were prepared in 60–90% chemical yield with the enantioselectivity ranging from 2 to 41%. 6,7-Dimethoxy-3,4-dihydroisoquinoline 8 was transformed into (+)-salsolidine 11 with an e.e. of 41%.

Enantioselective addition of organolithium reagents to 3,4-dihydroisoquinoline in the presence of (−)-sparteine as an external ligand. Application for the synthesis of isoquinoline alkaloids

Abstract Three isoquinoline alkaloids, (−)-salsolidine 2 , (+)-carnegine 6 and (−)-1-phenyl-2-methyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 7 , were obtained in high yield and with 17–46% e.e. by the enantioselective additions of organolithium reagents to dihydroisoquinolines 1 and 5 , in the presence of (−)-sparteine as a chiral ligand.

Enantioselective addition of organometallic compounds to 3,4-dihydroisoquinoline in the presence of oxazoline derivatives: synthesis of (R)-(+)- and (S)-(−)-salsolidine

The (R)- and (S)-enantiomers of salsolidine, 2, were prepared in good yield and moderate enantioselectivity (33 and 27% e.e., respectively) by the addition of methyllithium to 6,7-dimethoxy-3,4-dihydroisoqiunoline 1 in the presence of the chiral oxazoline ligands 4 and 10.

Synthesis of secoisoquinoline alkaloids total synthesis of peshawarine

Abstract In the total synthesis of (±)-peshawarine (1) hydrastinine derivative 6 was acylated with 1,3-dithian 7 applied as an acyl anion equivalent. The dithian masking group in addition product 8 was reductively removed using Raney nickel.

Addition reaction of O-toluamides with chiral auxiliary derived from 2-amino-1,3-propanediols to imines

Stereoselectivity of the addition reaction of o-toluamides, incorporating 2-amino-l,3-propanediols as chiral auxiliary to imines has been studied. Addition products, diastereomerically enriched, after column chromatography separation were obtained and further transformed to (S)-(-)-or (R)-(+)-8-oxoberbines with ee up to 97%.

Synthesis of secoisoquinoline alkaloids : Total synthesis of cryptopleurospermine

Abstract Cryptopleurospermine ( 1 ), a 1,2-secobenzylisoquinoline alkaloid was synthesized from hydrastinine derivative 2 and isovanillin 1,3-propylene dithioacetal 3 . The formation of C-C bond between these two synthons involved addition of dilithio salt of dithian 3 to aldehyde group in 2 . Reduction and hydrolysis of the masking group in addition product 4 furnished the synthesis.

(4S)-(−)-4-Benzyl-2,2-dimethyl-3-o-toluoyl-1,3-oxazolidine

The absolute configuration of the title compound, C20H23NO2, has been confirmed as 4S. The benzyl residue and H atom at the asymmetric C-atom centre occupy pseudo-axial and bisectional positions, respectively. The oxazolidine ring adopts an envelope conformation. In the crystal structure, the molecular packing is stabilized by non-classical C—H⋯O hydrogen bonds.