Pavel A. Krasutsky

Triterpene derivatives that inhibit human immunodeficiency virus type 1 replication

Triterpene derivatives were analyzed for anti-HIV-1 activity and for cellular toxicity. Betulinic aldehyde, betulinic nitrile, and morolic acid derivatives were identified to have anti-HIV-1 activity. These derivatives inhibit a late step in virus replication, likely virus maturation.

Lanthanide shift reagents as a structural probe for alkenes

Abstract The utility of LSR for structural analysis of the AG + complexes of 3,7-dimethylenebicyclo[3.3.1]nonane and its derivatives is demonstrated.

Dimethylaminopyridine derivatives of lupane triterpenoids cause mitochondrial disruption and induce the permeability transition

Triterpenoids are a large class of naturally occurring compounds, and some potentially interesting as anticancer agents have been found to target mitochondria. The objective of the present work was to investigate the mechanisms of mitochondrial toxicity induced by novel dimethylaminopyridine (DMAP) derivatives of pentacyclic triterpenes, which were previously shown to inhibit the growth of melanoma cells in vitro. MCF-7, Hs 578T and BJ cell lines, as well as isolated hepatic mitochondria, were used to investigate direct mitochondrial effects. On isolated mitochondrial hepatic fractions, respiratory parameters, mitochondrial transmembrane electric potential, induction of the mitochondrial permeability transition (MPT) pore and ion transport-dependent osmotic swelling were measured. Our results indicate that the DMAP triterpenoid derivatives lead to fragmentation and depolarization of the mitochondrial network in situ, and to inhibition of uncoupled respiration, induction of the permeability transition pore and depolarization of isolated hepatic mitochondria. The results show that mitochondrial toxicity is an important component of the biological interaction of DMAP derivatives, which can explain the effects observed in cancer cells.

Dimethylaminopyridine derivatives of lupane triterpenoids are potent disruptors of mitochondrial structure and function

Development of mitochondrially-targeted drugs is receiving increasing attention because of the central roles these organelles play in energy production, reactive oxygen generation, and regulation of cell death pathways. Previous studies have demonstrated that both natural and synthetic triterpenoids can disrupt mitochondrial structure and function. In this study, we tested the ability of a number of dimethylaminopyridine (DMAP) derivatives of lupane triterpenoids to target mitochochondria in two human melanoma cell lines and an untransformed normal fibroblast line. These compounds induced a striking fragmentation and depolarization of the mitochondrial network, along with an inhibition of cell proliferation. A range of potencies among these compounds was noted, which was correlated with the number, position, and orientation of the DMAP groups. Overall, the extent of proliferation inhibition mirrored the effectiveness of mitochondrial disruption. Thus, DMAP derivatives of lupane triterpenoids can be potent mitochondrial perturbants that appear to suppress cell growth primarily via their mitochondrial effects.

New derivatives of lupane triterpenoids disturb breast cancer mitochondria and induce cell death

Novel cationic dimethylaminopyridine derivatives of pentacyclic triterpenes were previously described to promote mitochondrial depolarization and cell death in breast and melanoma cell lines. The objective of this work was to further investigate in detail the mechanism of mitochondrial perturbations, correlating those effects with breast cancer cell responses to those same agents. Initially, a panel of tumor and non-tumor cell lines was grown in high-glucose or glucose-free glutamine-containing media, the later forcing cells to synthesize ATP by oxidative phosphorylation only. Cell proliferation, cell cycle, cell death and mitochondrial membrane polarization were evaluated. Inhibition of cell proliferation was observed, accompanied by an arrest in the G1-cell cycle phase, and importantly, by loss of mitochondrial membrane potential. On a later time-point, caspase-9 and 3 activation were observed, resulting in cell death. For the majority of test compounds, we determined that cell toxicity was augmented in the galactose media. To investigate direct evidences on mitochondria isolated rat liver mitochondria were used. The results showed that the compounds were strong inducers of the permeability transition pore. Confirming our previous results, this work shows that the novel DMAP derivatives strongly interact with mitochondria, resulting in pro-apoptotic signaling and cell death.

A NEW ONE-STEP METHOD FOR OXAADAMANTANE SYNTHESIS

Oxidation of 2-methyl-2-hydroxyadamantane by trifluoroperacetic acid in trifluoroacetic acid gives oxaadamantane and exo-2-oxaadamantane-4-ol in a good yield. Other 2-hydroxyadamantane derivatives do not undergo this transformation. An oxidative cleavage and subsequent cyclization mechanism is proposed.

The carbon-hydrogen insertion reaction of dichlorocarbene with polycyclic hydrocarbons.☆

Abstract The factors influencing the carbon-hydrogen insertion reaction of dichlorocarbene into tertiary carbon-hydrogen bonds are discussed.

On the reaction of alcohols with halocarbenes. Are carbocations intermediates

Abstract There is no evidence for hydride shift in the reaction of alcohols 1 and 2 with dichlorocarbene. Accordingly, the intermediate cannot be a free carbocation. It is suggested that the products are formed through a combination of S N i and direct displacement reactions in which tight ion pairs are involved.

Oxidative addition to 3,6-dehydrohomoadamantane

Abstract Transformations of 3,6-dehydrohomoadamantane ( 1 ) and 1,3-dehydroadamantane ( 2 ) with nitronium reagents were studied. In the case of compound 1 an oxidative route of reaction is realized resulting in addition of two nucleophiles from reagent or solvent to the strained CC bond. Contrary to this, compound 2 in the same conditions undergoes an electrophilic addition reaction. Transformations of 3,6-Dehydrohomoadamantane ( 1 ) and 1,3-Dehydroadamantane ( 2 ) under treatment with nitronium reagents were studied. In the case of compound 1 the oxidative route of the reaction is realized resulting in addition of two nucleophiles from reagent or solvent to the strained CC bond. Contrary to this, compound 2 in the same conditions undergoes an electrophilic addition reaction.

Stereoselectivity of A-ring contraction for 3-oxotriterpenoids

The A-ring oxidation/contraction of 3-oxotriterpenoids was developed as a two-step and “one pot” process. A benzylic acid type rearrangement of triterpenoid diosphenols gives (S)- as major and (R)-α-hydroxycarboxylic acids as minor reaction products. The absolute configurations were determined from the X-ray crystal structure analysis. The mechanism of ring contraction was modelled computationally at the DFT and MP2 levels of theory. The tautomeric triterpenoid A-seco δ-oxocarboxylic acids and A-ring hydroxy lactones formed after deep oxidation/acidification of 3-oxotriterpenoids.