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- W2951997787 abstract "A new and simple method has been developed for preparation of -methylene cyclopentenones and presently provides most convenient route to sarkomycin. The work has, in addition, led to a better understanding of vinylogous Dieckmann condensation, course of Michael addition to -methylene cyclopentenones and behavior of endocyclic and exocyclic dienolates towards electrophi es. INTRODUCTION The chemistry of cyclopentenoid antibiotics,1 a small class of compounds isolated from culture broth of streptomyces species, has recently attracted much attention from chemists. 2 Despite success of existing methods, there have been recent reports on various alternative approaches to synthesis of nucleus, reflecting strong interest in this significant unit which is also found in a variety of other biologically important naturally occurring compounds. The work about to be described is from part of an on-going program being carried out in our laboratory. A THREE-CARBON ANN ELATION ROUTE TO CYCLOPENTENONES A few years ago we came across a very simple and effective method for construction of disubstituted cyclopentenones (e.g. 4 or 5) via a three-carbon annelation as outlined below 3 (Scheme 1). Scheme 1 R4 R3 R4 R3 R4 R3 R4 R2 1. LDA LDA ? 1 S#)._( R1',rCOOEt 2 .BrfR4 (X.COOEt R'>< 1 2 orThF/NEDA 3 4 The mechanism of above annelation is regarded as involving rapid cyclisation of allyl anion 3. Various attempts to trap anion 3 have failed, reaction directly giving 4 and/or its thermodynamically more stable product 5. Recognizing its potential, we decided to use above reaction for synthesis of -methylene cyclopentenones 6, including methylenomycin B and the deceptive sarkomycin Now, up until that time all syntheses of -methylene cyclopentenones have invariably involved two compulsory steps: construction of five-membered ring and subsequent formation of exo-methylene group via an elimination reaction (Figure A). In our study, however, desired sequence was achieved by simply reacting propene unit with a masked -methylene carbonyl function (Figure B, Scheme 2, and Table 1). 781" @default.
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- W2951997787 date "1986-10-14" @default.
- W2951997787 modified "2023-09-25" @default.
- W2951997787 title "ChemInform Abstract: Synthesis and Chemistry of Cyclopentenoid Antibiotics" @default.
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- W2951997787 doi "https://doi.org/10.1002/chin.198641349" @default.
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