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Bis-THF acetogenins

The use of iodoetherification has been exploited in the synthesis of precursors to mono- and bis-THF acetogenins,234 potent antitumor and pesticides. Also, has been used in the synthesis of tetrahydrofuran analogs of precursors to pseudomonic acid.235 As well, N1S has been used as the iodine source, for example in the synthesis of other acetogenins.236 Other compounds synthesized via iodocyclization include ( )-(a)-multistriatin,237 ( )-velbanamine, and ( )-isovalbanamine,238 and (+)-citreoviral.239... [Pg.55]

Figure 15. Ambiguity Exists (cf., 27a vs. 27b) in the Relative Configuration Between Internal Carbinol Centers in All non-Adjacent bis-THF Acetogenins (B3). Figure 15. Ambiguity Exists (cf., 27a vs. 27b) in the Relative Configuration Between Internal Carbinol Centers in All non-Adjacent bis-THF Acetogenins (B3).
Table i. Adjacent Bis-THF Acetogenins Isolated From Formosan Annonaceous Plants... [Pg.981]

Figure 6. Twelve (of Twenty Possible) Diastereomeric, Synthetic, Model Compounds for the bis-THF Core of B1 Acetogenins. Figure 6. Twelve (of Twenty Possible) Diastereomeric, Synthetic, Model Compounds for the bis-THF Core of B1 Acetogenins.
To confirm the applicability of this method to the tetrahydrofuran portion of the Annonaceous acetogenins, the symmetric model bis-THF 18, where both C(15) and C(24) were known to be R, was synthesized and converted to the (S)- and (fl)-MTPA esters, S-MTPA-18 and /7-MTPA-18.21 The chemical shift differences of selected protons in these diastereomeric esters are shown in Figure 11. As expected, the sign of... [Pg.265]

A year later, Cassady published the synthesis and study of a set of model compounds representing the full spectrum of possible stereochemical relationships in dihydroxylated mono-THF acetogenins. Six mesitoylated compounds (23a-f, Fig. 13) were synthesized and subjected to H NMR spectroscopic studies. In these bis-mesitoates, good correlation between the relative configuration and the chemical shifts of selected protons was observed (Table 6). Specifically, It was found that ... [Pg.267]

The Annonaceous acetogenins offer a unique mode of action (ATP depletion) against MDR tumors and against insecticide-resistant pests and are predicted to become important future means of thwarting ATP-depleting-resistance mechanisms. Their SARs in several systems have been determined (Landolt et al., 1995 Alfonso et al., 1996 He et al., 1997 Oberlies et al., 1997 Miyoshi et al., 1998) and optimum structural features generally point to the bis-adjacent THF compounds such as bullatacin (1) and asimicin (2). [Pg.187]

In 1991, Hoye was the first to report the total synthesis of an acetogenin /rexepr -uvaricin 90, which has in common with natural uvaricin the right relative configuration across the THF skeleton but is of the opposite absolute configuration (2). The strategy used as a key step the asymmetric epoxidation of a homochiral bis-allylic alcohol, which allowed 5 out of 6 stereocentres to be built up at once with the desired relative configuration. A few more steps were necessary for the inversion of the last stereocenter (Fig. 10). [Pg.207]

Roblot et al. (63) were the first to report the hemi-synthesis of a natural acetogenin of Annonaceae. They have shown that treatment of a natural precursor, diepomuricanin-A 121, by NaOH followed by acetylation with Ac20-pyridine afforded solamin diacetate 155 in 60 % yield. Unfortunately the composition of the expected diastereomeric mixture was not discussed. Indeed opening of the bis-epoxide system at either C-15 or C-20 would lead to two different compounds 155 and 156 with the same relative configuration but of opposite absolute configuration across the THF ring (Fig. 23). [Pg.219]

Our observations appear to be consistent with Landolt s findings, in which they indicated that acetogenins with the bis-adjacent THF ring or the bis-nonadjacent THF ring are about ten times more active than those with the mono-THF ring after a more complete research in screening 20 acetogenins by mitochondrial inhibition assay in 1995 [81]. [Pg.991]


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See also in sourсe #XX -- [ Pg.270 ]

See also in sourсe #XX -- [ Pg.17 , Pg.270 ]

See also in sourсe #XX -- [ Pg.17 , Pg.270 ]




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