Addition to steroid polyenes—II Reaction of 7-dehydrocholesteryl acetate with dimethyl acetylenedicarboxylate

Dimethyl acetylenedicarboxylate reacts with 7-dehydrocholesteryl acetate (I) by nucleophilic addition at C₇. Two products are obtained, resulting from subsequent hydrogen abstraction from C₉ (II) and from C₁₄ (III) respectively. Addition-abstraction, hitherto unreported for esters of acetylenedicarboxylic acid, appears to be the sole reaction mode with this highly hindered diene-system. Structure proof is supported by NMR spectroscopy as well as by chemical transformations of the adducts. On treatment with base one of the adducts undergoes a prototropic rearrangement.     

An effective [1,4]-charge affinity inversion of sulfur functionalized isoprenes

Consecutive [1,2]- and [1,3]-migrations of the sulfur functionality convert the hydroxysulfoxide terpene building block 1a into the charge affinity inverted synthon 6 or the desulfurized chloro aldehyde 9a.     

Suppression of soft nuclear bremsstrahlung in proton-nucleus collisions

Photon energy spectra up to the kinematic limit have been measured in 190 MeV proton reactions with light and heavy nuclei to investigate the influence of the multiple-scattering process on the photon production. Relative to the predictions of models based on a quasifree production mechanism, a strong suppression of bremsstrahlung is observed in the low-energy region of the photon spectrum. We attribute this effect to the interference of photon amplitudes due to multiple scattering of nucleons in the nuclear medium.     

Controlling single-photon Fock-state propagation through opaque scattering media

The control of light scattering is essential in many quantum optical experiments. Wavefront shaping is a technique used for ultimate control over wave propagation through multiple-scattering media by adaptive manipulation of incident waves. We control the propagation of single-photon Fock states through opaque scattering media by spatial phase modulation of the incident wavefront. We enhance the probability that a single photon arrives in a target output mode with a factor 30. Our proof-of-principle experiment shows that the propagation of quantum light through multiple-scattering media can be controlled, with prospective applications in quantum communication and quantum cryptography.