Spectroscopic, morphological, and mechanistic investigation of the solvent-promoted aggregation of porphyrins modified in meso-positions by glucosylated steroids.

Solvent-driven aggregation of a series of porphyrin derivatives was studied by UV/Vis and circular dichroism spectroscopy. The porphyrins are characterised by the presence in the meso positions of steroidal moieties further conjugated with glucosyl groups. The presence of these groups makes the investigated macrocycles amphiphilic and soluble in aqueous solvent, namely, dimethyl acetamide/water.

Triterpenoid pyrazines and benzopyrazines with cytotoxic activity.

Twelve lupane, 18alpha-oleanane, and des-E-lupane derivatives (1a-5b) were either extracted from natural sources or synthesized from betulinic acid (1a) and betulin (2). Compounds 1b, 1c, 3b, 3c, 4b, 4c, 5a, and 5b were then used as starting materials for further synthesis of a series of pyrazines and benzopyrazines (6a-18); 20 of them are new (6a-6e, 7a-7d, and 10a-18). Activity of pyrazine 6a against the T-lymphoblastic leukemia cell line CEM encouraged us to synthesize several new esters (6b-6d) to study structure-activity relationships with respect to substitution of the carboxyl group at position 28.

Simple preparation of 3I-O-substituted beta-cyclodextrin derivatives using cinnamyl bromide.

[reaction: see text] A new method for preparation of 3(I)-O-substituted beta-cyclodextrin derivatives was developed. Cinnamyl bromide reacts with beta-cyclodextrin to form predominantly the 3(I)-O-cinnamyl derivative (30% isolated yield, >90% regioselectivity). After protection of the remaining cyclodextrin hydroxyls by acetylation, the cinnamyl group can be easily transformed to many other groups (exemplified by transformation to 3(I)-O-carboxymethyl derivative).

Influence of esterification and modification of A-ring in a group of lupane acids on their cytotoxicity.

The aim of this work was to find an optimal ester group for preparation of lupane derivatives connecting high cytotoxicity with good chemical and pharmacological properties. Activities of methyl-, pivaloyloxymethyl- (Pom-), and acetoxymethyl- (Acm-) esters were compared with the activity of free acids. Although the methyl- and Pom-esters were generally less active than free acids, some Acm-esters had cytotoxicity similar to or even better than the starting compounds.

Cocyclotrimerization of 6-alkynylpurines with alpha,omega-diynes as a novel approach to biologically active 6-arylpurines.

Transition metal complex catalyzed cocyclotrimerization of 6-alkynylpurines 1 with various diynes enables the preparation of a plethora of substituted 6-arylpurines 3 in good yields. The most general catalyst for the reaction is a user-friendly system based on a nickel-phosphine complex and reductant (NiBr(2)(dppe)/Zn) in MeCN. The reaction conditions are compatible with various protective groups on the purine moiety (Bn, THP).

2,8'-disubstituted-1,1'-binaphthyls: a new pattern in chiral ligands.

The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions.