Danuta Mostowicz

New optically pure sugar hydroperoxides. Synhtesis and use for enantioselective oxygen transfer

Abstract 2-Deoxy-2-C-methylene methyl glycosides undergo oxidation with hydrogen peroxide in the presence of molybdenum trioxide as catalyst to afford the corresponding anomeric hydroperoxides. These hydroperoxides were used as chiral oxidants of allylic alcohols and prochiral sulfides to offer moderate enantioselectivities which were, however, higher than those reported before oxidation with optically active peroxyacids.

Oxidation of Glycals with Hydrogen Peroxide

Tri-O-acetyl-D-glucal (8) treated with a mixture of hydrogen peroxide–molybdenum trioxide undergoes a Ferrier rearrangement to form 2,3-unsaturated anomeric hydroperoxides 14 and 15. Tri-O-acetyl-D-galactal (10) and tri-O-benzyl-D-glucal (9), under the same conditions, afford the hydroperoxides in a low yield, whereas tri-O-benzyl-D-galactal (11) does not produce any unsaturated hydroperoxide. 2,3-Unsaturated anomeric hydroperoxides of α- and β-D-erythro- and α-D-threo-19, -20, and -24, respectively, were used for the enantioselective epoxidation of prochiral allylic alcohols 25-27 and oxidation of sulfides 28 and 29 to give stereoselectivities of up to 50% enantiomeric excess.

Synthesis of enantiopure 1,2-dihydroxyhexahydropyrroloisoquinolines as potential tools for asymmetric catalysis

Abstract The stereocontrolled synthesis of enantiopure 1,2-dihydroxyhexahydropyrroloisoquinolines 2–4 and a formal synthesis of ent-2–4 starting from d -mannose and l -tartaric acid is reported. The strong tertiary amine bases 2–4 containing hydroxyl groups, able to activate electrophiles through hydrogen bonding, are potentially useful as a catalysts in base-catalyzed processes as well as new ligands in metal-based catalysis.

High- and atmospheric-pressure cycloaddition of trichloroacetyl isocyanate to 3,4-di-O-acetyl-L-rhamnal

Abstract High- and atmospheric-pressure cycloaddition of trichloroacetyl isocyanate ( 2 ) to 3,4-di-O-acetyl-L-rhamnal ( 11 ) leads to formation of four products: α-gluco (4+2) cycloadduct 12 , two stereoisomeric α-gluco 13 and β-manno 14 (2+2) cycloadducts, and α,β-unsaturated amide 15 . The isocyanate enters the rhamnal molecule preferentially anti with respect to the 3-O-acetyl substituent. It is found that under conditions of both - high and normal pressure (4+2)cycloaddition is preferred over (2+2) cycloaddition, more so under high pressure. Under normal pressure, better stereoselectivity in (2+2) cycloaddition is obtained. Elevation of temperature and prolongation of the reaction time promote rearrangement to α,β-unsaturated amide. Transformations of the reaction products into N-unsubstltuted: 1-O-tri-chloroacetyl compound 20 , methyl glycosides 23 and 24 , β-lactam 25 , α,β-unsaturated amide 26 , and into the 4-aza-2,10-dioxabicyclo(4.2.0)decan-5-one skeleton 16 – 19 are described.

Heck Cyclization Strategy for Preparation of Erythrinan Alkaloids: Asymmetric Synthesis of Unnatural (−)-Erysotramidine from L-Tartaric Acid

With an imide derived from L-tartaric acid as the starting material, ent-erysotramidine was synthesized for the first time. The synthesis features the use of the enantiopure synthon, prepared in a set of highly stereoselective reactions, including N-acyliminium cyclization, dihydrofuranyl ring formation via silver-catalyzed intramolecular alcohol addition to acetylene, and vinyl ether catalytic hydrogen reduction. The crucial step of the synthesis, assembly of ring A, was achieved by using Heck cyclization of (Z)-iodoolefin.

Synthesis of 2-Carbamoyl-2-Deoxy Glycosides

Abstract Recently we have reported the addition of trichloracetyl isocuyanate to glycals 1 1,2,3. The reaction led to the highly stereoselective formation of a mixture of unstable [2+2] and [4+2] cycloadducts 2 and 3. The isocyanate adds to the glycal moiety anti to the substituent at C-3. The addition of benzylamine to the reac6tion mixture led to N-deprotection of 2 and allowed us to isolate stable bicyclic β-lactams 4 1-3. We have shown also that 2 (a mixture of α-L-gluco and β-L-manno isomers) obtained from L-rhamnal 1 (R1[dbnd]Ac, R2[dbnd]CH3 under high pressure, when treated with methanol, underwent a rapid trans opening of the four-membered ring to give respective glycosides 5(β-L-gluco and α-L-manno isomers). On the other hand 3 (R1[dbnd]Ac, R2[dbnd]CH3) under the same conditions added a molecule of methanol to the C[dbnd]N double bond affording 6.

Novel route to β-lactam systems

The reactions of carbodiimides with a Reformatsky reagent give 4-iminoazetidin-2-ones in 51–88% yield.

Oxaziridine synthesis by asymmetric induction

Chiral substituents on nitrogen in Schiff bases induce oxidation to give oxaziridines with a high degree of stereospecificity when the bases are treated with organic peroxy-acids.

Conformations of 2-C:1-N-carbonyl-2-deoxy-D-glycopyranosylamines

Geometry and molecular conformation of theN-toluenesulfonyl1 andN-acetyl-2 derivatives of peracetylated 2-C:1-N-carbonyl-2-deoxy-α-d-glucopyranosylamine were investigated with the use of X-ray diffraction methods. Compound1 (C20H23NSO10) crystallizes in the monoclinic P21 space group, withZ=2 anda=8.238(1),b=7.988(1),c=16.928(2)Å, β=99.12(1)°. Compound2 (C15H19NO9) crystallizes in orthorhombic P212121 space group withZ=4 anda=8.385(1),b=8.550(1),c=24.000(2) Å. Analysis of differences in bond lengths and angles between compounds1 and2 and other compounds of this class showed that the electronwithdawing effect by the residue located at the nitrogen atom can be manifested by lengthening of the β-lactam C-N bonds, with simultaneous shortening of the distance between two carbon atoms at the ring fusion. Semi-empirical calculations suggested that the title compounds displayed two positively charged centers, susceptible for attack of nucleophiles, one at the carbonyl group of β-lactam and the second at the anomeric carbon atom. Atomic charges, however, calculated for compounds1 and2 did not explain their different reaction directions during alcoholysis.