{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/19961"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/19961","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The total syntheses of (+)-crotanecine, (-)-hastanecine and (-)-rosmarinecine utilizing the tandem (4+2)/(3+2) cycloadditions of nitroalkenes","abstract":"A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.","abstract_html":"A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.","abstract_has_math":true,"creators":["Thorarensen, Atli"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry, Organic","degree_department":null,"school":null,"contributors":["Denmark, Scott E."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T12:24:17Z","date_published":"2011-05-07T12:24:17Z","updated_at":"2026-07-22T22:25:15Z","subjects":["Chemistry, Organic"],"languages":["eng"],"rights":["Copyright 1996 Thorarensen, Atli"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["9780591199413","AAI9712459","(UMI)AAI9712459"],"render_values":[{"text":"9780591199413","href":null,"code":true},{"text":"AAI9712459","href":null,"code":true},{"text":"(UMI)AAI9712459","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/19961","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Denmark, Scott E."]},{"key":"dc:creator","label":"Author","values":["Thorarensen, Atli"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T12:24:17Z","10000-01-01","1996"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry, Organic"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Organic"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1996 Thorarensen, Atli"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["9780591199413","AAI9712459","(UMI)AAI9712459","http://hdl.handle.net/2142/19961"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.","(${-}$)-Rosmarinecine 42 is the necine base portion of the pyrrolizidine alkaloid (${-}$)-rosmarinine. (${-}$)-Rosmarinecine is a representative of that group of pyrrolizidines which bear a cis relationship between adjacent stereocenters C(1), C(7) and C(7a) in addition to a highly oxygenated skeleton. (${-}$)-Rosmarinecine has been synthesized in 8 steps and 14.8% overall yield, as an illustration of a general approach for the construction of pyrrolizidines bearing this stereochemical feature. The key step in the asymmetric synthesis is a Lewis acid-promoted, tandem inter (4+2) /intra (3+2) cycloaddition between a fumaroyloxynitroalkene 165 and a chiral vinyl ether (${-}$)-29.","Numerous alkaloids contain (+)-crotanecine 36 as it necine constituent. (+)-Crotanecine which is an all cis substituted necine has been prepared in 10 steps and 10.2% overall yield. The key steps in the asymmetric synthesis is a Lewis acid-promoted, tandem inter (4+2) /intra (3+2) cycloaddition between a fumaroyloxynitroalkene 165 and a chiral propenyl ether (${-}$)-222 and a solvolytic elimination of a mesylate to install the unsaturation at C(6)-C(7).","Made available in DSpace on 2011-05-07T12:24:17Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9712459.pdf: 11700756 bytes, checksum: ee60140bbcc9a76d78ad527a16169fc5 (MD5) Previous issue date: 1996","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:40:36Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:17:26-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["The total syntheses of (+)-crotanecine, (-)-hastanecine and (-)-rosmarinecine utilizing the tandem (4+2)/(3+2) cycloadditions of nitroalkenes"]}]}],"canonical_facts":{"dc:contributor":["Denmark, Scott E."],"dc:creator":["Thorarensen, Atli"],"dc:date":["2011-05-07T12:24:17Z","10000-01-01","1996"],"dc:description":["A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.","(${-}$)-Rosmarinecine 42 is the necine base portion of the pyrrolizidine alkaloid (${-}$)-rosmarinine. (${-}$)-Rosmarinecine is a representative of that group of pyrrolizidines which bear a cis relationship between adjacent stereocenters C(1), C(7) and C(7a) in addition to a highly oxygenated skeleton. (${-}$)-Rosmarinecine has been synthesized in 8 steps and 14.8% overall yield, as an illustration of a general approach for the construction of pyrrolizidines bearing this stereochemical feature. The key step in the asymmetric synthesis is a Lewis acid-promoted, tandem inter (4+2) /intra (3+2) cycloaddition between a fumaroyloxynitroalkene 165 and a chiral vinyl ether (${-}$)-29.","Numerous alkaloids contain (+)-crotanecine 36 as it necine constituent. (+)-Crotanecine which is an all cis substituted necine has been prepared in 10 steps and 10.2% overall yield. The key steps in the asymmetric synthesis is a Lewis acid-promoted, tandem inter (4+2) /intra (3+2) cycloaddition between a fumaroyloxynitroalkene 165 and a chiral propenyl ether (${-}$)-222 and a solvolytic elimination of a mesylate to install the unsaturation at C(6)-C(7).","Made available in DSpace on 2011-05-07T12:24:17Z (GMT). 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