Commun., 15 (1966); T . Nozoe, T. Mukai. K. Takase, and T. Nagase. Roc. Jpn. Acad., 28, 477 (1952). (23) The situation is analogous to that encountered in the condensation of 1-diethylaminobutadiene with fulvenes: L. C. Dunn, Y.-M. Chang. and K. N . Houk, J. Am. Chem. SOC., 98,7095 (1976). (24) C. J. Weber, J. Bo/. Chem., 76, 465 (1928). (25) High-resolution mass spectra were measured in the National Institutes of Health supported facility at Massachusetts Institute of Technology (Grant FR 00317) under the direction of Professor K. Biemann. Dr. Catherine E. Costello deserves special thanks for her efforts.Abstract: The monomeric base macroline 5, previously utilized in biomimetic syntheses of the Alstonia bisindole alkaloids villalstonine ( l ) , alstonisidine (2), macralstonine (3), and macralstonidine (4), was converted to the monomeric alkaloid alstonerine (10) by a n epoxidation-dehydration sequence. Alstonerine (10) was converted by reduction followed by acid-catalyzed rearrangement into Nb-methyl-Nb,2 1 -secotalpinine (20), and alstonisine (21) into talpinine (18) by twofold reductive rearrangement. Model experiments bearing upon these interconversions are described. The nature of the biogenetic "macroline equivalent" is discussed in the light of these results. During model reactions performed to develop a biomimetic pathway to the pyridinoindole base suaveoline (30), a new, potentially general synthesis of 2-alkyl-and 3-alkylpyridines, utilizing dihydropyran as starting material, was developedIn previous work in our laboratory, the Alstonia bisindole alkaloids villalstonine ( 1),2 alstonisidine (2),2 macralstonine (3),3 and macralstonidine (4)4 were synthesized by acid-cat-H,COOC H 1 -3 4alyzed Michael-type and vinylogous Michael-type reactions between macroline 5 and respectively pleiocarpamine ( 6 ) , quebrachidine (7), alstophylline (8), and N,-methylsarpagine (9). Although macroline itself has not been encountered as a natural product, the notable directness and stereospecificity of these syntheses have led us to consider macroline or a n "equivalent" as a likely biogenetic precursor of the bisindoles 1-4, and to regard the syntheses therefore as biomimetic. In this paper we report our work on biomimetic transformations 0002-7863/78/1500-4213$01.00/0 H3C"0 e, R = OCH, . R' = CH, IO; R = H, R ' = CH, H I 9 --24, R = H, R' : COCF, -25; R = H, R' : COCH, -among some monomeric alkaloids. First we consider alkaloids closely related to macroline itself by virtue of carbon skeleton and natural occurrence, and then we discuss interconversions connecting the macroline bases with other indole alkaloids so as to suggest the likelihood of biogenetic relationships.Alstophylline (8) and alstonerine (10) are the known alkaloids closest to macroline ( 5 ) , so we investigated first the conversion 5 -. 10. In view of the importance of Michael-type reactions in the bisindole syntheses, we envisaged a Michaeltype ring closure of macroline followed by dehydrogenation to give 10. Macroline was recovered unchanged after exp...
Villalstonine (1) and alstonisidine (25) have been synthesized from macroline (3) and, respectively, pleiocarpamine (2) and quebrachidine (8). These syntheses are stereospecific and biomimetic, and represent the first syntheses of any kind in this group of bisindole alkaloids. In the case of alstonisidine, this synthesis, with investigations of model compounds, permits revision of the earlier proposed structure 7 to the isomeric 25. Villalstonine (l)3•4 is the major alkaloid of Alstonia muellerianaf A. macrophylla,3•4•6 and A. spectabilis6 C = A. somersetensis, = A. villosa).1 Structure 1, being a "bisindole," can be envisaged as arising biogenetically by reaction of two "monomeric" indole alkaloids. The elegant chemical work of Schmid and his co-workers4 included the degradation of villalstonine to the known alkaloid pleiocarpamine (2) and the hitherto unknown base macroline (3). Macroline has not yet l H been found as such in nature, but it can clearly be regarded as a possible biogenetic precursor of the known "monomeric" Alstonia alkaloids alstonerine (4),8 alii) Portions of this work have been published in preliminary form:
The major cytotoxic activity of crude extracts of Nectandra rigida Nees is due to dehydrodiisoeugenol,the sample isolated being slightly enriched in the dextrorotatory enantiomer. Galgravin and two new tetrahydrofuranoid lignans, nectandrin A and nectandrin B, were also isolated and characterized along with small quantities of vanillin, 2,6-dimethoxybenzoquinone, and the known lauraceous alkaloid laurelliptine. The neolignans are of potential chemotaxonomic significance in the study of the Lauraceae.
The flowers of the Mexican tree Quararibea funebris (Llave) Vischer (Bombacaceae) have been shown to give rise to the enolic 7-lactone 1, its amino analogue 3, the saturated lactone 4, and the parent amino acid (2S,3S,4R)-7-hydroxyisoleucine (5), as well as the novel pyrrole alkaloid funebrine (6). The structure determination of funebrine by X-ray crystallography is discussed and a hypothesis for its biogenesis offered.
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