B. de Lange

Dynamic Control and Amplification of Molecular Chirality by Circular Polarized Light

The enantiomers of a racemic photoresponsive material represent two distinct states that can be modulated with irradiation at a single wavelength by changing the handedness ofthe light. Dynamic control over molecular chirality was obtained by the interconversion of enantiomers of helically shaped molecules with either left or right circular polarized light (CPL). Photoresolution of the bistable compound as a dopant in a nematic liquid crystalline phase by CPL irradiation led to a chiral mesoscopic phase. The chiral information inherent to CPL is therefore transmitted to the bistable molecule, followed by amplification and macroscopic expression of the chirality.

Asymmetric 1,4-Additions to 5-Alkoxy-2(5H)-furanones Enantioselective Synthesis and Absolute Configuration Determination of β-Amino-γ-butyrolactones and Amino Diols

Abstract The synthesis of enantiomerically pure β-amino-δ-butyrolactones via asymmetric conjugate addition of various amines to 5-menthyloxy-2(5H)-furanone is described. This route provides access to new multifunctionalhomochiral building blocks. The absolute configuration of the β-amino-δ-butyrolactones is established by X-ray analysis and 1H NMR correlation. Theconjugate addition of amines to 2[5H]-furanone, 5-alkyl-2[5H]-furanones and 5-alkoxy-2[5H]-furanones was studied and an enhanced reactivity was observed in 2[5H]-furanones due to a γ-alkoxy-effect. The synthetic utility of the asymmetric amine addition is illustrated in an efficient route to various optically pure 2-amino-1, 4-butanediols.

Asymmetric Synthesis of 2-Amino-1,4-diols

Abstract Diastereoselective addition of amines to (1)-5-menthyloxy-2-(5H)-furanone yields aminolactones that upon reduction with LiAlH4 provide enantiomerically pure aminodiols.

1,3-DIPOLAR CYCLOADDITIONS TO 5-METHOXY-2(5H)-FURANONE

Abstract Various nitrile oxides and nitrones, ethyl diazoacetate and an azomethine ylide were examined in 1,3-dipolar cycloadditions to 5-methoxy-2[5H]-furanone, in particular with respect to regio- and diastereoselectivities. Isoxazoles 13–17 and isoxazolidines 21, 22 and 24 were obtained in high yields with anti-facial selectivities and regioselectivities exceeding 95%. In the case of pyrazoline 26 minor amounts of syn-facial adduct are also observed, whereas lactone annulated pyrrolidines 28 are obtained as mixtures of regio-isomers.