Covadonga Astorga

Sequential biocatalytic resolution of (±)-trans-cyclohexane-1,2-diamine. Chemoenzymatic synthesis of an optically active polyamine

Candida antarctica lipase-catalysed double monoaminolysis of dimethyl malonate by (±)-trans-cyclohexane-1,2-diamine allows the sequential resolution of the latter compound, affording an enantiopure bis(amidoester), (R,R)-3, which is subsequently transformed into an optically active polyamine, (R,R)-9.

Enzymatic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol and (±)-cis- and (±)-trans-2-aminoindan-1-ol

Abstract Pseudomonas cepacia lipase (PSL) efficiently catalyses the kinetic resolution of (±)- cis - and (±)- trans -1-aminoindan-2-ol through the O- acylation reaction of the corresponding N -benzyloxycarbonyl derivative using vinyl acetate as the acyl donor. In a similar way, cis - N -Cbz-2-aminoindan-1-ol is resolved when isopropenyl acetate is used as the acylating agent. The enantioselectivity of the reaction was lower for (±)- trans - N -Cbz-2-aminoindan-1-ol due to the different steric requirements for the two conformers of this substrate.

Enzymatic resolution of (±)-trans-2-aminocyclohexanol and (±)-trans-2-aminocyclopentanol

Abstract Candida antarctica lipase (CAL) catalyzes the resolution of (±)- trans -2-aminocyclohexanol by alkoxycarbonylation or acylation reactions. Besides, N -benzyloxycarbonyl derivatives of (±)- trans -2-aminocyclohexanol and (±)- trans -2-aminocyclopentanol are efficiently resolved through O -acylation by Pseudomonas cepacia lipase (PSL).

Enzymatic resolution of (±)-cis-2-aminocyclopentanol and (±)-cis-2-aminocyclohexanol

Abstract (±)- cis - N -Benzyloxycarbonyl-2-aminocyclopentanol was efficiently resolved by O -acylation with Pseudomonas cepacia lipase, as was (±)- cis-N -benzyloxycarbonyl-2-aminocyclohexanol when Candida antarctica lipase was used.

Optically active tetraazamacrocycles analogous to cyclam

Abstract The syntheses of enantiopure tetraazamacrocycles analogous to cyclam, ( S , S )- 3 , ( R , R )- 3 and ( S , S , S , S )- 4 , have been carried out. NMR and semiempirical studies of 3 have revealed that this compound presents a rigid conformation with C 2 symmetry, which is stabilized by intramolecular bifurcated hydrogen bonds. Structural studies for macrocycle 4 have shown that the presence of two cyclohexane rings of ( S , S ) configuration leads to the loss of the D 2 symmetry in solution, which is in agreement with the AM1 calculated structure.

Enzymatic Selective Transformations of Diethyl Fumarate

Abstract Candida antarctica lipase selectively catalyses transformations of diethyl fumarate in organic solvents. A range of nitrogen nucleophiles, including ammonia, can be succesfully used in these enzymatic reactions, monoamides and monohydrazides being obtained in high to moderate yields. In contrast, diethyl maleate is not an adequate substrate for this enzyme.

Enzymatic aminolysis of non-activated diesters with diamines

Selective aminolysis of diesters is catalysed by Candida antarctica lipase. Using this enzymatic reaction N,N′-polymethylenesuccinimides and N,N′-polymethyleneglutarimides can be obtained. When propane-1,2-diamine is used as the nucleophile, the enzyme catalyses the aminolysis of diesters with very good enantioselectivity.

CHEMOENZYMATIC SYNTHESES OF POLYAMINES AND TETRAAZAMACROCYCLES

ABSTRACT Syntheses of different open chain polyamines starting from enzymatically prepared bis(amidoesters) are described. Some of these polyamines are also used as precursors in the syntheses of tetraazamacrocycles. This methodology can also be applied to the synthesis of chiral compounds.

Structural studies of two protonated forms of a C2 symmetrical optically active cyclam derivative

Detailed structural analyses, including solid-state (X-Ray), solution-state (NMR) and theoretical (AM1) studies of the two most stable protonated forms — di 3H22+ and tetraprotonated 3H44+ — of a C2 symmetrical, optically active cyclam derivative 3 have been carried out. Important conformational changes in the 14-membered and cyclohexane rings accompany the protonation. A rigid conformation with C2 symmetry stabilized by bifurcated intramolecular hydrogen bonds is obtained for 3H22+, whereas for 3H44+ a dynamic system in solution and a loss of the C2 symmetry in the solid state are found. The effects of temperature and the counter-ion are also discussed.