Combinatorial Chemistry for Ligand Development in Catalysis: Synthesis and Catalysis Screening of Peptidosulfonamide Tweezers on the Solid Phase

On the basis of a pyrrolidine tweezer 1, a library of peptidosulfonamide tweezers (15a-e, 16a-e) was synthesized on the solid phase. This library was screened in a simultaneous substrate screening procedure for the ability to enantioselectively catalyze the Ti(O-i-Pr)(4)-mediated addition of diethylzinc to aldehydes. One of the best solid-phase tweezer catalyst (i.e., 16d, giving an ee of 32% in solid-phase catalysis) was resynthesized in solution (compounds 20 and 21). The now homogeneous solution-phase catalysis showed even better enantioselectivity (i.e., up to 66%).     

Generation of 60-nJ sub-40-fs pulses at 70 MHz repetition rate from a Ti:sapphire chirped pulse-oscillator

We have studied the influence of the intracavity dispersion on the mode-locking characteristics of pure-Kerr-lens mode-locked Ti:sapphire chirped-pulse oscillators. Using the results of this study, we have built chirped-pulse oscillators that can be mode-locked when pumped with the highest pump powers commercially available at 532 nm. We generated 62 nJ pulses at 70 MHz repetition rate, with a Fourier limited duration of 33 fs. PACS 42.60.Fc; 42.60.Lh; 42.65.Re