- Unusual Bromination of Tetrahydro-(-)-α-santonins and New Santonin Isomers: X-Ray Crystal and Molecular Structure of 2β,14-Dibromo-4α,5β,6β,11βH-tetrahydrosantonin
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A novel bromination-dehydrobromination reaction of tetrahydro-(-)-α-santonins is reported which has led, via the 2α,14- and 2β,14-dibromo ketones (2a,b), to two new dienone isomers of (-)-α-santonin whose structures were established by X-ray diffraction and c.d. studies of (2b).
- Inayama, Seiichi,Shimizu, Nobuko,Shibata, Tetuichi,Hori, Hitoshi,Iitaka, Yoichi
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- Synthetic approach to exo-endo cross-conjugated cyclohexadienones and its application to the syntheses of dehydrobrachylaenolide, isodehydrochamaecynone, and trans-isodehydrochamaecynone
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Methodology for synthesis of exo-endo cross-conjugated dienones with trans- and cis-decalin systems has been reported. Bromination of the silyl enol ether of α′-methyl α,β-unsaturated ketones with PTAB and successive dehydrobromination of the resulting α′-bromo-α′-methyl α,β-unsaturated ketones under three conditions (DBU/PhH; TBAF/THF; Li2CO3, LiBr/DMF) gave the desired exo-endo cross-conjugated dienones in good yield. This method was applied to the syntheses of dehydrobrachylaenolide (1), isodehydro-chamaecynone (5c), and trans-isodehydrochamaecynone (11) starting from tuberiferine (7), chamaecynone (5a), and trans-chamaecynone (9). Eudesmanolides possessing an α-methylene γ-lactone moiety, i.e., 1, 7, and 13, exhibited significant inhibitory activity toward the induction of the intercellular adhesion molecule-1 (ICAM-1). Compound 1 showed greater activity than 7 and 13. All compounds possessing an ethynyl group, 5d, 9, 11, and 14, showed the same degree of termiticidal activity, and the exo-endo cross-conjugated dienone structure in 11 had no influence on the activity.
- Higuchi, Yohsuke,Shimoma, Fumito,Koyanagi, Rei,Suda, Kouji,Mitsui, Tomokazu,Kataoka, Takao,Nagai, Kazuo,Ando, Masayoshi
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p. 588 - 594
(2007/10/03)
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- Synthesis of elemane bis-lactones from santonin - Synthesis of the reported structure of seco-isoerivanin pseudo acid and formal synthesis of (+)-8-deoxyvernolepin
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The synthesis of the reported structure for seco-isoerivanin pseudo acid (1) and of an elemane bis-lactone 5 from santonin (4) through a common vinylic precursor 12 is described. Compound 5 is a known intermediate in a previous synthesis of the antitumor compound (+)-8-deoxyvernolepin (3). The vinyl group of 12 underwent a regio- and diastereoselective anti addition of an external electrophile and an intramolecular condensation to yield either the selenolactone 13 or the hydroxylactone 17. The lactones 13 and 17 served as key intermediates in the total synthesis of 1 and 5 respectively. A revision of the structure of seco-isoerivanin pseudo acid to the C-10 epimer is suggested on the basis of comparison between the spectral data of the natural and synthetic products.
- Blay, Gonzalo,Cardona, Luz,Garcia, Begona,Lahoz, Luisa,Pedro, Jose R.
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p. 2145 - 2151
(2007/10/03)
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- A short-step synthesis of sesquiterpene lactone, 1-oxoeudesma-2,4-dien-11βh-12, 6α-olide, isolated from artemisia herba-alba and its derivatives
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1-Oxoeudesma-2,4-dien-11βH-12,6α-olide(1) isolated from the genus Artemisia herb-alba was synthesized from α-santonin in a two-step sequence. The key step is the 1,3 oxidative rearrangement of dienol 7.
- Kawamata,Nagashima,Nakai,Tsuji
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p. 139 - 148
(2007/10/03)
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- A formal synthesis of l-α-santonin from chiral α,β-epoxyeudesmanolide via enzyme-catalyzed hydrolysis
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(4S,5R)-Epoxy-(3S)-hydroxy-(10S)-7α,11βH-eudesman-6α,12-olide 4 and (4R,5S)-epoxy-(3S)-hydroxy-(10R)-7β,11αH-eudesman-6β,12-olide 5 were obtained from (±)-3 using yeast and (3S)-acetoxy-(4S,5R)-epoxy-(10S)- 7α,11βH-eudesman-6α,12-olide 8 was produced from (±)-8 using lipase, respectively. New total synthesis of l-α-santonin (9), and its Δ(4(14))- isomers (10 and 11) were accomplished by a short step synthesis using the optically active key intermediate (10S)-8 (prepared by asymmetric hydrolysis of (±)-8).
- Shimizu,Akita,Oishi,Inayama
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p. 1160 - 1162
(2007/10/02)
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- Synthetic Transformation of Santonin into (5α,7α,11β)-3,6-Dioxogermacr-1-en-13,7-olide, a New Intermediate for Germacranes and Guaianes
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A seven-step synthesis of a new intermediate (5α,7α,11β)-3,6-dioxogermacr-1-en-13,7-olide (10) is described starting from (-)-α-santonin (1).The key step in the transformation was photolytic skeletal rearrangement of (4α,5β,6α,11β)-5-hydroxy-2-oxoeudesman-13,6-olide (9) to the title compound, sensitised by mercuric oxide and iodine.
- Harapanhalli, Ravi S.
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p. 1009 - 1012
(2007/10/02)
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- The chemistry of thujone. XI. Thujone as a chiral synthon for the preparation of sesquiterpene lactones. Synthesis of (l)-α-santonin
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An efficient synthesis of (l)-α-santonin is described.The thujone-derived trienone 1, bearing only one chiral center, is transformed, via a controlled hydroboration process, to the isomeric triols 7 and 9 in which four new chiral centers (C-3, C-6, C-7, and C-11) are established in one step and with the correct absolute configuration.An oxidative cyclization process converts 7 and 9 into 1,2-dihydro-6α-santonin (3), with the latter being transformed directly to the natural product employing DDQ as a dehydrogenating agent.The overall strategy reveals an attractive synthetic entry into the family of natural sesquiterpene lactones.
- Kutney, James P.,Singh, Ashok K.
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p. 2813 - 2817
(2007/10/02)
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- Stereochemistry of Microbial Hydrogenation of (-)-α-Santonin to (+)-1,2-Dihydro-α-santonin by Streptomyces cinereocrocatus NRRL 3443
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The stereochemistry of microbial transformation of (-)-α-santonin (1) by Streptomyces cinereocrocatus is described.Fermentation of (-)-α-santonin (1) with S. cinereocrocatus led to the formation of (+)-1,2-dihydro-α-santonin (2).To elucidate the stereochemistry of the microbial hydrogenation of (-)-α-santonin, (-)-2H>-α-santonin (1a) was synthesized from 1, and subjected to the microbial transformation.Analysis of the 400 MHz proton nuclear magnetic resonance spectrum of the deuterated product clearly revealed that the microbial hydrogenation of 1a proceeds stereo-specifically with trans-addition of hydrogens via si face attacks at the 1 and 2 positions. Keywords - microbial transformation; Streptomyces cinereocrocatus; (-)-α-santonin; deuterated (-)-α-santonin; (+)-1,2-dihydro-α-santonin; stereochemistry; si face attack
- Sato, Yoshihiro,Oda, Taiko,Inoue, Junko,Kunugi, Masayuki,Suzuki, Kazuo T.
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p. 504 - 509
(2007/10/02)
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- THE TOTAL SYNTHESIS OF 1-OXYGENATED EUDESMANOLIDES
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A route towards 1-oxygenated eudesmanolides, via a (2+2) photocycloaddition reaction for constructing the decalin framework is described.The following natural substances have been synthesized. (+/-)-dihydroreynosin (1), (+/-)-1-oxo-dihydromagnolialide (2)
- Hijfte, Luc Van,Vandewalle, Maurits
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p. 4371 - 4382
(2007/10/02)
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- Biogenetic-type Synthesis of Santonin, Chrysanolide, Dihydrochrysanolide, Tulirinol, Arbusculin-C, Tanacetin, and Artemin
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The title compounds were synthsised from their possible biogenetic precursors through hydroperoxide intermediates generated by photo-oxygenation.This route for biological oxygenation may serve as a substitute to epoxidation.The 13C n.m.r. special assignments for all intermediates were made.Single-crystal X-ray analyses unequivocally established the 1S configuration in dihydrochrysanolide (14) and its hydroperoxy-analogue (12).Isomorphous crystals of (12) and (14) belong to the monoclinic system, space group P21, with a = 14.350(6), b = 5.882(3), c = 10.343(3) Angstroem, β = 107.64(2) deg, Z = 2, for (12), and a = 14.461(6), b = 5.887(3), c = 9.698(4) Angstroem, β = 107.44(2) deg, Z = 2, for (14).Least-squares refinement of atomic parameters converged to R 0.040 for (12) and 0.033 for (14) over 1484 and 1300 reflections, respectively, measured by diffractometer.
- El-Feraly, Farouk S.,Benigni, Daniel A.,McPhail, Andrew T.
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p. 355 - 364
(2007/10/02)
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- Preparation, Decarboxylation and Absolute Configuration of (+)-11α-Carboxy- and (+)-11β-Carboxy-3α,4β,5α,6βH-hexahydrosantonin, and (-)-11β-Carboxysantonin
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A simple and stereoselective preparation of (-)-11β-carboxysantonin (8a) was achieved by carboxylation of l-α-santonin (5b), based on the non-stereoselective two-step method described earlier. (+)-11β-Carboxy- (3a) and (+)-11α-carboxy-3α,4β,5α,6βH-hexahydrosantonin (3b) were prepared in a ratio of 3:1 by alkoxycarbonylation of 3α,4β,5α,6β,11βH-hexahydrosantonin (HHS) (1a), followed by hydrolysis. The absolute configurations at C-11 in the three optically active 11-carboxysantonins have now been confirmed on the basis of the stereochemistry of the fourth new stereoisomer, (-)-11β-carboxysantonin (8a).The complete structure of 8a was established by its transformation to (+)-11β-carboxy-4β,5α,6βH-tetrahydrosantonin (7a), correlating with 3a.The proton magnetic resonance (PMR) signals of 6β-hydrogens in 11β-carboxy- or 11β-methoxycarbonyl-HHS (2a-4a) are anisotropically shifted further downfield compared to those in the 11α-oriented epimers (2b-4b).A similar result was obtained for the pairs of epimers in the 4β,5α,6β,11βH-tetrahydrosantonin (THS) series (6a,7a and 6b,7b). The stereospecific decarboxylation of the 11β- and 11α-carboxylactone derivatives (3a,7a,8a and 3b,7b,8b) afforded the thermodynamically more stable 11α-methyl lactone analogs (1a,5a,5b), and not the 11β-methyl epimers (1c,5c,5d).The rate of decarboxylation of the former lactone acids was faster than that of the latter, supporting the foregoing assignments, based on spectral data, for the configurations of the 11β- and 11α-carboxyl groups. Keywords---(-)-11β-carboxysantonin; (+)-11β-carboxysantonin; (-)-11α-carboxysantonin; (+)-11α-carboxysantonin; (+/-)-11β-carboxysantonin; (+/-)-11α-carboxysantonin; (+)-11β-carboxy-3α,4β,5αH-hexahydrosantonin; (+)-11α-carboxy-3α,4β,5αH-hexahydrosantonin; stereoselective preparation; stereospecific decarboxylation
- Inayama, Seiichi,Kawamata, Takeshi,Hirose, Tadaaki
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p. 288 - 295
(2007/10/02)
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