A New Enantioselective Total Synthesis of Natural Vincamine  via  an Intramolecular  Mannich  Reaction of an Silyl Enol Ether | Zendy

Oppolzer Wolfgang | Zendy; Hauth Hartmut | Zendy; Pfäffli Paul | Zendy; Wenger Roland | Zendy

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A New Enantioselective Total Synthesis of Natural Vincamine via an Intramolecular Mannich Reaction of an Silyl Enol Ether

Author(s) -

Oppolzer Wolfgang,

Hauth Hartmut,

Pfäffli Paul,

Wenger Roland

Publication year - 1977

Publication title -

helvetica chimica acta

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.74

H-Index - 82

eISSN - 1522-2675

pISSN - 0018-019X

DOI - 10.1002/hlca.19770600533

Subject(s) - chemistry , intramolecular force , enantioselective synthesis , silyl enol ether , enol , mannich reaction , silylation , organic chemistry , stereochemistry , medicinal chemistry , combinatorial chemistry , catalysis

Natural Vincamine ( 1 ) has been synthesized in an enantioselective manner starting from the ethylpentenal 7 . In the key step a mixture of the diastereoisomeric racemates, 14 and 15 , was directly obtained from the silyl enol ether 11 and the dihydro‐β‐carboline 12 by the way of an intramolecular Mannich reaction of the intermediate 13 (Scheme 4) . The undesired stereoisomers, 14 and 15b , were recycled to 15a using the related reversible Mannich reaction 18 ⇄ 14 + 15 , followed by crystallization of the salt from 15a and (+)malic acid. 15a was converted to natural vincamine ( 1 ) in several steps including the known transformation 20→1 .

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