The copper-catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn-chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5. The potential of this approach was illustrated by the preparation of two consecutive all-carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from -35 to -20 °C to avoid subsequent fragmentation reaction into stereodefined β,γ-nonconjugated unsaturated esters 4. Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[Cu]. Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti-selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn-3 and anti-3 can be obtained, at will, from the same precursor cyclopropenyl esters 1.
The diastereoselective carbocupration reaction of cyclopropenylmethyl ethers followed by addition of oxenoid leads to the formation of diastereo- and enantiomerically enriched 2,2,3,3-tetrasubstituted cyclopropanol derivatives. Ring fragmentation of the copper cyclopropanolate leads to acyclic butenal derivatives possessing enantiomerically enriched α-quaternary carbon stereocenters in a single-pot operation.
The transcription of the luminescence (lux) system of Vibriofischeri is regulated by the LuxR protein and an autoinducer. We previously showed that apart from these regulatory elements, the transcription of the lux system is negatively controlled by the LexA protein and positively controlled by the HtpR protein (C32 The pioneering work of Engebrecht et al. (8) and Engebrecht and Silverman (9) revealed that the Vibrio fischeni luminescence system is encoded by a gene cluster with a divergent transcription pattern. The leftward promoter (PL) controls the formation of the regulatory protein (LuxR), while the right promoter (PR) controls the formation of six polypeptides, three of which (LuxC, LuxD, and LuxE) are required for the formation of the long-chain aldehyde (2). Two polypeptides (LuxA and LuxB) form luciferase, and one polypeptide (LuxI) is responsible for the formation of the autoinducer. It has been shown that the transcription of luxR is activated by the cyclic AMP (cAMP) receptor protein in the presence of cAMP (5, 6).The regulation of light production by the luminous bacterium V. fischeri has been extensively studied (1,8,9,20).According to the presently accepted model, light production in V. fischeri is controlled by a mechanism called autoinduction. V. fischeni produces a diffusible substance, termed autoinducer [N-(3-ketocaproyl) homoserine lactone] (7), that accumulates in the medium during growth. The model suggests that when the concentration of the inducer reaches a few molecules per cell, the synthesis of luciferase and other enzymes involved in luminescence is induced (15). Ulitzur and Kuhn (25) have shown that at least two other regulatory elements are involved in the transcriptional control of the luminescence system. A consensus binding site for the LexA protein has been found in the -35 region of PR.It was also demonstrated that the HtpR protein (a32) is involved in the regulation of the luminescence system in Escherichia coli cells harboring the whole lux system of V.
The catalytic asymmetric carbometalation of cyclopropenes followed by either an electrophilic oxidation or amination reaction provides a unique approach to the formation of diastereomerically pure and enantiomerically enriched cyclopropanol and cyclopropylamine derivatives, respectively.
The distant functionalization of ω-ene cyclopropanols is induced by a Pd-catalyzed Heck reaction triggering a "metal-walk" and selective ring-opening of the three-membered ring. This approach provides a new class of acyclic aldehydes possessing concomitantly a stereodefined double bond and a quaternary carbon stereocenter α to the carbonyl group.
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