Matches in SemOpenAlex for { <https://semopenalex.org/work/W1973223887> ?p ?o ?g. }
- W1973223887 endingPage "185" @default.
- W1973223887 startingPage "176" @default.
- W1973223887 abstract "The first asymmetric synthesis of alpha-amino acids based on diastereoselective carbon radical addition to glyoxylic imine derivatives is reported. The addition of an isopropyl radical, generated from i-PrI, Bu(3)SnH, and Et(3)B in CH(2)Cl(2) at 25 degrees C, to achiral glyoxylic oxime ether 1 proceeded regioselectively at the imino carbon atom of the oxime ether group to give an excellent yield of the C-isopropylated product 2. The competitive reaction using glyoxylic oxime ether 1 and aldoxime ether 4 showed that the reactivity of the glyoxylic oxime ether toward nucleophilic carbon radicals was enhanced by the presence of a neighboring electron-withdrawing substituent. Thus, the alkyl radical addition to glyoxylic oxime ether 1 proceeded smoothly even at -78 degrees C, in contrast to the unactivated aldoxime ether 4. A high degree of stereocontrol in the carbon radical addition to the glyoxylic oxime ether was achieved by using Oppolzer's camphorsultam as a chiral auxiliary. The stannyl radical-mediated reaction of the camphorsultam derivative 6 with an isopropyl radical at -78 degrees C afforded a 96:4 diastereomeric mixture, 7a, of the C-isopropylated product. The reductive removal of the benzyloxy group of the major diastereomer (R)-7a, by treatment with Mo(CO)(6) and the subsequent removal of the sultam auxiliary by standard hydrolysis, afforded the enantiomerically pure D-valine (R)-12 without any loss of stereochemical purity. To evaluate the new methodology, a variety of alkyl radicals were employed in the addition reaction which gave the alkylated products 7 with excellent diastereoselectivity, allowing access to a wide range of enantiomerically pure natural and unnatural alpha-amino acids. Even in the absence of Bu(3)SnH, treatment of 6 with alkyl iodide and Et(3)B at 20 degrees C gave the C-alkylated products 7 with moderate diastereoselectivities. The use of Et(2)Zn as a radical initiator, instead of Et(3)B, was also effective for the radical reaction. The enantioselective isopropyl radical addition to 1 using (R)-(+)-2, 2'-isopropylidenebis(4-phenyl-2-oxazoline) and MgBr(2) gave excellent chemical yield of the valine derivative 2 in 52% ee." @default.
- W1973223887 created "2016-06-24" @default.
- W1973223887 creator A5000278321 @default.
- W1973223887 creator A5043849731 @default.
- W1973223887 creator A5060721672 @default.
- W1973223887 creator A5062383807 @default.
- W1973223887 creator A5076437541 @default.
- W1973223887 date "1999-12-16" @default.
- W1973223887 modified "2023-09-27" @default.
- W1973223887 title "Asymmetric Synthesis of α-Amino Acids Based on Carbon Radical Addition to Glyoxylic Oxime Ether" @default.
- W1973223887 cites W1967884198 @default.
- W1973223887 cites W1969833996 @default.
- W1973223887 cites W1975167675 @default.
- W1973223887 cites W1978888563 @default.
- W1973223887 cites W1979510333 @default.
- W1973223887 cites W1979813209 @default.
- W1973223887 cites W1982232619 @default.
- W1973223887 cites W1982450534 @default.
- W1973223887 cites W1985895666 @default.
- W1973223887 cites W1991145461 @default.
- W1973223887 cites W1993031474 @default.
- W1973223887 cites W1993041693 @default.
- W1973223887 cites W2008077878 @default.
- W1973223887 cites W2013771571 @default.
- W1973223887 cites W2021375811 @default.
- W1973223887 cites W2023349655 @default.
- W1973223887 cites W2033027497 @default.
- W1973223887 cites W2053891675 @default.
- W1973223887 cites W2057717450 @default.
- W1973223887 cites W2082329495 @default.
- W1973223887 cites W2082497851 @default.
- W1973223887 cites W2101372620 @default.
- W1973223887 cites W2105184044 @default.
- W1973223887 cites W2112432470 @default.
- W1973223887 cites W2163989583 @default.
- W1973223887 cites W2949845394 @default.
- W1973223887 cites W2950365301 @default.
- W1973223887 cites W2950533303 @default.
- W1973223887 cites W2951779544 @default.
- W1973223887 cites W2951916932 @default.
- W1973223887 cites W2952274998 @default.
- W1973223887 cites W2953224771 @default.
- W1973223887 doi "https://doi.org/10.1021/jo991353n" @default.
- W1973223887 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/10813913" @default.
- W1973223887 hasPublicationYear "1999" @default.
- W1973223887 type Work @default.
- W1973223887 sameAs 1973223887 @default.
- W1973223887 citedByCount "123" @default.
- W1973223887 countsByYear W19732238872012 @default.
- W1973223887 countsByYear W19732238872013 @default.
- W1973223887 countsByYear W19732238872014 @default.
- W1973223887 countsByYear W19732238872015 @default.
- W1973223887 countsByYear W19732238872017 @default.
- W1973223887 countsByYear W19732238872019 @default.
- W1973223887 countsByYear W19732238872020 @default.
- W1973223887 countsByYear W19732238872021 @default.
- W1973223887 countsByYear W19732238872023 @default.
- W1973223887 crossrefType "journal-article" @default.
- W1973223887 hasAuthorship W1973223887A5000278321 @default.
- W1973223887 hasAuthorship W1973223887A5043849731 @default.
- W1973223887 hasAuthorship W1973223887A5060721672 @default.
- W1973223887 hasAuthorship W1973223887A5062383807 @default.
- W1973223887 hasAuthorship W1973223887A5076437541 @default.
- W1973223887 hasConcept C104264131 @default.
- W1973223887 hasConcept C138716334 @default.
- W1973223887 hasConcept C146686406 @default.
- W1973223887 hasConcept C155647269 @default.
- W1973223887 hasConcept C161790260 @default.
- W1973223887 hasConcept C178790620 @default.
- W1973223887 hasConcept C185592680 @default.
- W1973223887 hasConcept C2776573223 @default.
- W1973223887 hasConcept C2779061078 @default.
- W1973223887 hasConcept C2779489543 @default.
- W1973223887 hasConcept C2779648554 @default.
- W1973223887 hasConcept C2780407432 @default.
- W1973223887 hasConcept C71240020 @default.
- W1973223887 hasConceptScore W1973223887C104264131 @default.
- W1973223887 hasConceptScore W1973223887C138716334 @default.
- W1973223887 hasConceptScore W1973223887C146686406 @default.
- W1973223887 hasConceptScore W1973223887C155647269 @default.
- W1973223887 hasConceptScore W1973223887C161790260 @default.
- W1973223887 hasConceptScore W1973223887C178790620 @default.
- W1973223887 hasConceptScore W1973223887C185592680 @default.
- W1973223887 hasConceptScore W1973223887C2776573223 @default.
- W1973223887 hasConceptScore W1973223887C2779061078 @default.
- W1973223887 hasConceptScore W1973223887C2779489543 @default.
- W1973223887 hasConceptScore W1973223887C2779648554 @default.
- W1973223887 hasConceptScore W1973223887C2780407432 @default.
- W1973223887 hasConceptScore W1973223887C71240020 @default.
- W1973223887 hasIssue "1" @default.
- W1973223887 hasLocation W19732238871 @default.
- W1973223887 hasLocation W19732238872 @default.
- W1973223887 hasOpenAccess W1973223887 @default.
- W1973223887 hasPrimaryLocation W19732238871 @default.
- W1973223887 hasRelatedWork W1973223887 @default.
- W1973223887 hasRelatedWork W1992719595 @default.
- W1973223887 hasRelatedWork W2019571757 @default.
- W1973223887 hasRelatedWork W2038415249 @default.