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Total Synthesis of Strychnos and Asp...

Kokkonda, Praveen.

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Total Synthesis of Strychnos and Aspidospermatan Alkaloids.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Total Synthesis of Strychnos and Aspidospermatan Alkaloids./
Author:	Kokkonda, Praveen.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2017,
Description:	232 p.
Notes:	Source: Dissertation Abstracts International, Volume: 78-10(E), Section: B.
Contained By:	Dissertation Abstracts International78-10B(E).
Subject:	Organic chemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10273401
ISBN:	9781369794373

Total Synthesis of Strychnos and Aspidospermatan Alkaloids.
Kokkonda, Praveen.

Total Synthesis of Strychnos and Aspidospermatan Alkaloids. - Ann Arbor : ProQuest Dissertations & Theses, 2017 - 232 p.

Source: Dissertation Abstracts International, Volume: 78-10(E), Section: B.

Thesis (Ph.D.)--Temple University, 2017.

The Strychnos class of indole alkaloids contain a pyrrolo[2,3- d]carbazole ABCE tetracyclic framework. The second-generation ABCE tetracycle approach was employed in the total synthesis of (+/-)-20- epi-lochneridine and progress toward total synthesis of (+/-)-alstolucine B. The second-generation approach featured Mitsunobu activation of the hydroxyethyl group in a gramine intermediate followed by intramolecular aza-Baylis-Hillman reaction. The substrate for hydroboration was redesigned to (+/-)-18-desmethyl akuammicine (1,1-disubstituted double bond), since the hydroboration of trisubstituted alkenes afforded tertiary alcohol via Markovnikov addition. The key steps were n-Bu3SnH mediated cyclization reaction to accomplish D-ring, tert-butyl hypochlorite indoline oxidation, and anti-Markovnikov hydroboration to introduce a primary alcohol.

ISBN: 9781369794373Subjects--Topical Terms:

523952
Organic chemistry.

Total Synthesis of Strychnos and Aspidospermatan Alkaloids.
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100 1 $a Kokkonda, Praveen. $3 3286569
245 1 0 $a Total Synthesis of Strychnos and Aspidospermatan Alkaloids.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2017
300 $a 232 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-10(E), Section: B.
500 $a Adviser: Rodrigo B. Andrade.
502 $a Thesis (Ph.D.)--Temple University, 2017.
520 $a The Strychnos class of indole alkaloids contain a pyrrolo[2,3- d]carbazole ABCE tetracyclic framework. The second-generation ABCE tetracycle approach was employed in the total synthesis of (+/-)-20- epi-lochneridine and progress toward total synthesis of (+/-)-alstolucine B. The second-generation approach featured Mitsunobu activation of the hydroxyethyl group in a gramine intermediate followed by intramolecular aza-Baylis-Hillman reaction. The substrate for hydroboration was redesigned to (+/-)-18-desmethyl akuammicine (1,1-disubstituted double bond), since the hydroboration of trisubstituted alkenes afforded tertiary alcohol via Markovnikov addition. The key steps were n-Bu3SnH mediated cyclization reaction to accomplish D-ring, tert-butyl hypochlorite indoline oxidation, and anti-Markovnikov hydroboration to introduce a primary alcohol.
520 $a The total syntheses of Strychnos-Strychnos type bis-indole alkaloids (--)-leucoridine A and C were accomplished from the biomimetic dimerization of (?)-dihydrovalparicine. En route to (--)-dihydrovialparicine, known alkaloids (+)-geissoschizoline and (--)-dehydrogeissoschizoline were also prepared from commercially available N-tosyl indole 3-carboxaldehyde. Key steps comsisted of an in situ dimerization of (--)-dihydrovalparicine from (--)-1, 2-dehydrogeissoschizoline with trifluoroacetic acid in the presence of 4 A molecular sieves. Acid mediated ring-opening of the indolenine in (--)-leucoridine A to afford (--)-leucoridine C. DFT calculations were employed to elucidate the mechanism of dimerization, which suggested that a stepwise aza-Michael/spirocyclization sequence was preferred over the alternate hetero Diels-Alder cycloaddition reaction.
520 $a A novel domino Michael/Mannich [4+2] annulation method was applied for concise total synthesis of Aspidospermatan alkaloids (+)-20- epi-condyfoline and progress toward the total synthesis of (+)-condyfoline. The additional key steps consisted of a LiHMDS mediated cyclization to form D-ring, dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF) mediated spirocyclization to form pentacyclic thioether and indoline oxidation with MnO2.
590 $a School code: 0225.
650 4 $a Organic chemistry. $3 523952
690 $a 0490
710 2 $a Temple University. $b Chemistry. $3 1029985
773 0 $t Dissertation Abstracts International $g 78-10B(E).
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791 $a Ph.D.
792 $a 2017
793 $a English
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