- Stereocontrolled total syntheses of (±)-pisiferic acid and (±)-O-methylpisiferic acid
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A stereocontrolled approach to the construction of the angularly ester substituted trans-octahydrophenanthrene ring system related to diterpenes involving an aryl participated diazoketone cyclisation strategy is delineated. The tetrahydrophenanthrenone 7 was prepared from the tetralone 6 through the intermediates 13, 14, 16 and 17. The formyl derivative of 7 was treated with alkaline H2O2 to give the diacid 18 which was converted into the diazomethyl ketone 9. Aryl participated cyclisation of 9 afforded the enedione 10 which was stereoselectively converted into the keto-ester 11. The transformation of 11 into the diterpenes 1 and 4 has been efficiently accomplished.
- Pal, Subrata Kumar,Gupta, Pranab Dutta,Mukherjee, Debabrata
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p. 1765 - 1771
(2007/10/03)
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- A new total synthesis of (±)-pisiferic acid
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Starting from 6-isopropyl-7-methoxy-1-tetralone 2, a new synthesis of (±)-pisiferic acid 1 has been achieved. The salient features of the present synthesis are (i) facile conversion of 2 into the cis-fused octahydrophenanthrenone 5. (ii) efficient transformation of 5 into the triester 7, and (iii) conversion of 7 into 1 involving Dieckmann cyclisation as a key reaction.
- Gupta,Pal,Mukherjee
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p. 1033 - 1035
(2007/10/03)
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- Stereoselective partial synthesis of (+)-pisiferic acid
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(±)-Pisiferic acid (1), an antibiotic active against Gram-negative and Gram-positive bacteria, was synthesized starting from dehydroabietic acid (2) or abietic acid (26). The terpene ring system was functionalized and a Barton reaction used to oxidize Me(20). The intermediates of this photochemical reaction were isolated and characterized.
- Geiwiz,Haslinger
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p. 818 - 832
(2007/10/02)
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- Total Synthesis of (+/-)-Pisiferic Acid
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A total synthesis of (+/-)-pisiferic acid (1) has been achieved by utilising the keto ether (22) which, in turn, was prepared from the alcohol (14).Subjection of the keto ether (22) to three sequential reactions (formylation, Michael addition with methyl vinyl ketone, and intramolecular aldol condensation) provided the tricyclic ether (27) whose conversion into the methoxyabietatriene (32) was accomplished in four steps (ethoxycarbonylation, Grignard reaction with methyl-lithium, acid-catalysed dehydration, and methoxylation).Reaction of the methoxyabietatriene (32) with zinc, zinc iodide, and acetic acid produced (+/-)-pisiferol (2) which was finally converted into (+/-)-pisiferic acid (1).The ketone (34) was converted into the abietatriene (41) following exactly the same procedure adopted for the transformation of the keto ether (22) into the abietatriene (32).Hydroboration-oxidation of (41) followed by oxidation with Jones reagent and reduction with lithium aluminium hydride followed by transannular oxidation gave the abietatriene (36).
- Banerjee, Ajoy Kumar,Hurtado S., Hector,Laya M., Manuel,Acevedo, Julio C.,Alvarez G., Jaime
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p. 931 - 938
(2007/10/02)
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- SYNTHESIS OF (+/-)-2β,2O-EPOXY-12-METHOXYABIETA-8,11,13-TRIENE
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The synthesis of the titled compound (1) and its conversion to pisiferic acid (2) are described.
- Banerjee, Ajoy K.,Acevedo, Julio C.,Alvarez, G. Jaime
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p. 2047 - 2052
(2007/10/02)
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- Total Synthesis of (+/-)-Pisiferic Acid, Methyl (+/-)-Pisiferate, and (+/-)-Pisiferol
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Acid catalyzed cyclization of 4-(3-isopropyl-4-methoxyphenethyl)-3,5,5-trimethyl-2-cyclohexen-1-one afforded 12-methoxyabieta-8,11,13-trien-2-one and its cis-isomer.Both compounds were further converted into 12-methoxyabieta-8,11,13-trien-2β-ol, which was treated with lead tetraacetate in the presence of iodine to yield 2β,20-epoxy-12-methoxyabieta-8,11,13-triene.Ether cleavage of the 2β,20-epoxy compound with acetyl p-toluenesulfonate, followed by catalytic hydrogenation, afforded 20-acetoxy-12-methoxyabieta-8,11,13-triene (23).This was then converted into methyl 12-methoxyabieta-8,11,13-trien-20-oate (27) via methyl 12-methoxy-7-oxoabieta-8,11,13-trien-20-oate.Demethylation of 27 with AlBr3-EtSH gave pisiferic acid, but with AlCl3EtSH 27 was partially demethylated to give methyl pisiferate.The acetate 23 was also converted into pisiferol by demethylation and reduction
- Matsumoto, Takashi,Usui, Shuji
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p. 1599 - 1604
(2007/10/02)
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