G. A. Ellestad

Some new terpenoid metabolites from an unidentified fusarium species

Abstract Six new terpenoids of mixed biogenetic origin exhibiting anti- Tetrahymena pyriformis activity have been isolated from an unclassified Fusarium species designated LL-Z1272. The structures of these metabolites, named LL-Z1272α, β, γ, δ, e and ζ, are composed of an orcyl aldehyde unit condensed with a farnesyl side chain which in γ, δ, e and ζ, is terminally cyclized to a cyclohexanone ring. All but β and e contain a chlorine atom in the aromatic portion of the molecule.

Structures of methyl aldgarosides A and B obtained from the neutral macrolide antibiotic aldgamycin E

Abstract The methanolysis of aldgamycin E yields, in addition to methyl mycinoside, two anomeric carbonate containing methyl glycosides, A and B. The structures of the two carbonate sugars have been elucidated and found to belong to the D series.

Reactions of the trisulfide moiety in calicheamicin

Abstract Calicheamicin γ1I ( 1 ) reacts with Ph3P to form a dimeric trisulfide ( 3 ), MeSSMe, Ph3PS, and Ph3PO, as well as an aromatic degradation product ( 2 ). The oxygen of the Ph3PO is derived from O2. Calicheamicin also reacts with thiols to produce disulfides (eg. 4 ) with high selectivity. Dimeric trisulfide 3 is generated during this reaction.

Circular dichroism studies of calicheamicin-DNA interaction: Evidence for calicheamicin-induced DNA conformational change

Abstract Evidence from circular dichroism studies suggests that the binding of calicheamicin to DNA induces an optically detectable conformational change of B-f

Pyrimido[1,2-b]-1,2,4,5-tetrazin-6-ones as HCMV protease inhibitors: a new class of heterocycles with flavin-like redox properties.

The synthesis and biological activity of pyrimidotetrazin-6-ones against HCMV protease is described. The mechanism of action for these inhibitors is the oxidation of several cysteine residues to generate cross-linked enzyme.

Interaction of Calicheamicin with DNA

The interaction of the potent antitumor agent calicheamicin with DNA has been investigated by analyzing the cleavage of plasmids, restriction fragments, and synthetic dodecamers. Proton NMR analysis of the aromatized product from the reaction of calicheamicin with unlabeled and deuterium-labeled DNA has provided additional insight into the molecular events involved in strand cleavage by the diyne-ene moiety of this novel natural product.

A trimeric l-ristosamine-ammonia condensation-product

Abstract Three molecules of l -ristosamine (3-amino-2,3,6-trideoxy- l - ribo -hexopyranose) condense with one molecule of ammonia to give a stable compound [1.1′.1′′-(dodecahydro-1,4,7,9 b -tetrazaphenalene-2,5,8-trityl)tri-1,2-propanediol] reminiscent of the mode whereby formaldehyde and ammonia condense to form hexamethylenetetramine. The structure of the crystalline hexaacetate of this compound has been determined by X-ray crystallography. The mass-spectral fragmentation pattern and the 13 C-n.m.r. signals shown by the acetylated compound are assigned.