1159215-73-2Relevant articles and documents
Total synthesis of meloscine by a [2+2]-photocycloaddition/ring-expansion route
Selig, Philipp,Herdtweck, Eberhardt,Bach, Thorsten
experimental part, p. 3509 - 3525 (2010/01/11)
The unusual monoterpenoid indole alkaloid meloscine was synthesized starting from a protected aminoethylquinolone in 15 steps and an overall yield of 9%, employing a [2+2]-photocycloaddition as the stereochemistry defining key step. After the initial plan of a Wagner-Meerwein type rearrangement of a [4.2.0]- into a [3.3.0]-bicyclic substructure could not be realized, the required ring enlargement of a cyclobutane was eventually achieved by a retro-benzilic acid rearrangement. Generation of the central pyrrolidine ring was possible by a three-step reductive amination domino sequence. The final ring was built up by a ring-closing metathesis after the last quaternary stereocenter had been constructed by a Johnson-Claisen rearrangement. The synthesis was concluded by a selenylation-elimination sequence to build up the exocyclic vinyl group of meloscine. Using our methodology for enantioselective [2+2]-photocycloaddition mediated by a chiral complexation agent, the experimentally very simple synthesis could be performed in an enantioselective fashion (7% overall yield). The enantioselective synthesis of (+)-meloscine represents the first example of a natural product synthesis employing an enantioselective [2+2]-photocycloaddition as its key step, and illustrates nicely the synthetic potential of photochemical transformations for the construction of complex heterocyclic structures.
Enantioselective total synthesis of the Melodinus alkaloid (+)-meloscine
Selig, Philipp,Bach, Thorsten
scheme or table, p. 5082 - 5084 (2009/03/11)
(Chemical Equation Presented) Enantioselective synthesis in a new light: The template-controlled [2+2] photocycloaddition leading to product 1 is the first example of this type of reaction in natural product synthesis. In addition, a retrobenzilic acid rearrangement (→2), a Claisen rearrangement (→3), and a ring-closing metathesis played decisive roles in the synthesis of the alkaloid (+)-meloscine (4).
