Zobrazeno 1 - 10
of 315
pro vyhledávání: '"Mauri Lounasmaa"'
Publikováno v:
Tetrahedron. 54:14845-14858
19S-Hydroxytacamine (3) and 19R-hydroxytacamine (4) were prepared from cis hydroxyesters 7 and 8 via corresponding O-TMS esters 9 and 22. Comparison of the spectral data of isomers 3 and 4 with those of 19-hydroxytacamine from Tabernaemontana eglandu
Publikováno v:
Tetrahedron. 54:10205-10216
The role of the nitrogen lone pairs in the mechanism of the acid-catalysed epimerization of indolo[2,3- a ]quinolizidines is investigated using lactams as model compounds. Deethyleburnamonine ( 3 ) did not epimerize with trifluoroacetic acid (TFA), w
Publikováno v:
Tetrahedron. 54:4673-4678
Intramolecular aldol condensation of ketoaldehyde 8 affords three new compounds: enone 9 , hydroxyketone 10 , and enone 11 . Enone 9 possesses the ring system of (−)-voaketone ( 1 ), which is a skeletal rearrangement product of the indole alkaloid
Autor:
Mauri Lounasmaa
Publikováno v:
Current Organic Chemistry. 2:63-90
A reveiw, concerning the recent synthetic achievements of our laboratory, is presented. The results are mostly associated with the work on indole alkaloids of corynantheine and tacamine type. In the preparation of alkaloids of corynantheine type, the
Publikováno v:
Tetrahedron. 54:157-164
Base-catalysed epimerization of the easily accessible trans ester 3 at C-1 gives rise in good yield to the seemingly less stable cis ester 2, which can be converted into the indole alkaloid tacamonine (1) in three steps.
Publikováno v:
Tetrahedron Letters. 38:1455-1458
Direct addition of dimethyl malonate anion to a 1,4-conjugate iminium salt of 3-ethylindolo[2,3- a ]quinolizidine 4a (regenerated from the corresponding α-aminonitrile 4b ) afforded enamine 5. Catalytic hydrogenation of compound 5 led stereoselectiv
Autor:
Mauri Lounasmaa, Pirjo Hanhinen
Publikováno v:
Tetrahedron. 52:15225-15242
Attempts were made to apply the spontaneous “biogenetic-type cyclization” of van Tamelen to the preparation of the sarpagan ring system by utilizing indolo [2,3-a]quinolizidines 10, 11, 12, and 14 . The fact that the spontaneous “biogenetic-typ
Publikováno v:
Tetrahedron. 52:11361-11378
Total syntheses are described for seven tacamine-type indole alkaloids (1–7) found in Tabernaemontana eglandulosa. (±)-Tacamine (1), (±)-16-epitacamine (2), and (±)-apotacamine (3) were prepared from pentacyclic intermediates 18. Apotacamine (3)
Publikováno v:
Tetrahedron. 52:6803-6810
Publikováno v:
Planta Medica. 62:42-45
10-Methoxydihydrocorynantheol and 10-methoxycorynantheidol were synthesized from 5-methoxytryptophol and 3-acetylpyridine. (13)C-NMR data of the prepared compounds and their synthetic intermediates are given.