Albert T. Sneden

Rollinicin and isorollinicin, cytotoxic acetogenins from Rollinia papilionella

Abstract Rollinicin and isorollinicin, two new linear acetogenins bearing bistetrahydrofuran moieties and an α,β-unsaturated-γ-lactone, were isolated from roots of Rollinia papilionella. The structure elucidation of rollinicin and isorollinicin was achieved through interpretation of the 1H NMR, 13C NMR and high resolution mass spectra.

Neoisostegane, a new bisbenzocyclooctadiene lignan lactone from Steganotaeniaaraliacea hochst.

The structure of neoisostegane, 1, a new bisbenzocyclooctadiene lignan lactone was elucidated from its1H and13C NMR spectra and by chemical correlation with known steganes.

A short synthesis of (±)-2,5-epoxy-6(E),8(E)-megastigmadiene

(±)-2,5-Epoxy-6(E),8(E)-megastigmadiene 1 was synthesized in seven steps and 27% overall yield from 2-methylfuran. The Diels-Alder reaction of 2-methylfuran with 2-chloroacrylonitrile gave 2-chloro-2-cyano-1-methyl-7-oxabicyclo[2.2.1]hept-5-ene 5a as the major regioisomer. Hydrogenation of 5a followed by hydrolysis and alkylation provided the key intermediate, 1,3,3-trimethyl-7-oxabicyclo[2.2.1]heptan-2-one 4. The conjugated diene sidechain was then introduced via a Grignard reaction followed by formation and subsequent decomposition of the phenylurethane derivative 10 to give 1 and its 6(Z) isomer 2.

Normal- and bonded-phase liquid chromatography with photodiode array detection of maytansinoids

Abstract Maytansinoids obtained from Maytenus species are known as potential anti-cancer drugs. Investigation of new plant species for the presence of unknown maytansinoids as well as synthetic work requires a reliable analytical and semipreparative normal-phase separation which can distinguish between known and unknown compounds independently from retention times and which would be compatible to LC-MS interfacing for further studies. A thorough study of numerous maytansinoids on silica gel and on diol-, aminopropyl- and cyanopropyl-bonded phases, suggests a complex retention mechanism based on molecular size as well as on specific interaction with the stationary phase while limiting a selectivity effect of the mobile phase. Utilizing a Varian 9065 photodiode array detector a spectral library of the separated substances was generated. This library simplifies the identification of known compounds in a matrix of unknowns such as fractions of plant extracts even if baseline separation is not achieved. Unlike reversed-phase separations that have been described in the literature the presented method allows an easy sample recovery in a semipreparative separation.