An efficient synthesis of (±)-narwedine and (±)-galanthamine by an improved phenolic oxidative coupling.

Old problems, new ideas! The biomimetic phenol coupling of norbelladine derivatives such as 1 (Bn = benzyl) to form galanthamine (2), a drug used in the treatment of Alzheimer's disease, has been greatly improved by the use of the hypervalent-iodine oxidation reagent phenyliodine(III) bis(trifluoroacetate) (PIFA).

Determination of absolute configuration and biological activity of new immunosuppressants, mycestericins D, E, F and G.

Mycestericins D, E, F and G were isolated from the culture broth of Mycelia sterilia ATCC 20349 as potent immunosuppressants. Mycestericins F and G were identical with dihydromycestericins D and E, respectively. Their absolute configurations were determined by use of the modified MOSHER'S method and by comparison of the CD spectra of their benzoate derivatives with those of synthetic analogs. Mycestericins D, E, F and G suppressed the proliferation of lymphocytes in the mouse allogeneic mixed lymphocyte reaction.

Synthesis of new fluorescent nucleosides, 3-beta-D-ribofuranosylpyrazolo (3,2-i) purine derivatives and their cytotoxic activities.

The novel nucleosides 3-beta-D-ribofuranosylpyrazolo(3,2-i) purine (8) and their 9-substituted bromo, nitro and amino compounds (3, 6 and 11) have been prepared from a fully protected 3-beta-D-ribofuranosyl(3,2-i)purine-9-carboxyamide 1 by bromodeamidation (ipso bromination). Compounds 3, 8 and 11 exhibited antileukemic activity against mouse leukemia L5178Y cells in culture, while the 9-substituted nitro, ester and amide compounds (6, 12 and 13) showed no cytotoxicity.

Time-dependent inhibition of rat brain monoamine oxidase by an analogue of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 4-(4-chlorophenyl)-1,2,3,6-tetrahydropyridine.

Inhibitory effects of some MPTP and MPP+ analogues on rat brain MAO activity were studied to further clarify the structure-activity relationships of MPTP neurotoxicity. Of the analogues tested, 4-(4-chlorophenyl)-1,2,3,6-tetrahydropyridine (CPTP), 4-(4-chlorobenzyl)-pyridine (CBP), 4-benzylpyridine (BPY) and 4-benzylpiperidine (BPIP) dose-dependently inhibited both MAO-A and -B activities. CPTP, BPY and BPIP showed a higher MAO-A selectivity, while CBP was a selective MAO-B inhibitor. In preincubation studies, only CPTP greatly enhanced the degree of inhibition of MAO-B when the preincubation time was increased, but inhibition of MAO-A was not enhanced. Together with our previous MPTP and MPP+ analogue findings, the present results indicate that, in these chemical structures, a 4-phenyl-1,2,3,6-tetrahydropyridine ring is most essential for time-dependent inhibition of MAO. This chemical requirement is consistent with the ability to cause nigrostriatal dopaminergic neurotoxicity.

Inhibition of rat brain monoamine oxidase by some analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenylpyridinium ion.

To clarify the essential chemical structures of the neurotoxins, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its oxidized product, 1-methyl-4-phenylpyridinium ion (MPP+), that govern nigrostriatal dopamine neuron toxicity, interactions of several structurally related compounds of MPTP or MPP+ with monoamine oxidase (MAO) in rat forebrain homogenates were studied. Of the compounds tested, 4-phenyl-1,2,3,6-tetrahydropyridine (PTP), 4-phenylpyridine and 4-phenylpiperidine strongly and dose-dependently inhibited MAO-A and -B activity. Inhibition of PTP and 4-phenylpiperidine was MAO-A-selective, while that by 4-phenylpyridine was MAO-B-selective. Of these 3 compounds, only PTP time-dependently inhibited MAO-B, but not -A. Without preincubation, the modes of inhibition of MAO-A and -B by PTP were competitive. After 1 h preincubation, the mode of MAO-B inhibition changed to non-competitive, while inhibition of -A remained unchanged. PTP was oxidized by MAO-B, but not by -A, under these conditions. In contrast, 4-phenylpyridine and 4-phenylpiperidine were not substrates for either form of MAO in rat forebrain homogenates. These results, along with the other observations, indicate that PTP may essentially cause a neurotoxic effect on the nigrostriatal dopamine pathway.