Ps conversions

Hoft reported about the kinetic resolution of THPO (16b) by acylation catalyzed by different lipases (equation 12) °. Using lipases from Pseudomonas fluorescens, only low ee values were obtained even at high conversions of the hydroperoxide (best result after 96 hours with lipase PS conversion of 83% and ee of 37%). Better results were achieved by the same authors using pancreatin as a catalyst. With this lipase an ee of 96% could be obtained but only at high conversions (85%), so that the enantiomerically enriched (5 )-16b was isolated in poor yields (<20%). Unfortunately, this procedure was limited to secondary hydroperoxides. With tertiary 1-methyl-1-phenylpropyl hydroperoxide (17a) or 1-cyclohexyl-1-phenylethyl hydroperoxide (17b) no reaction was observed. The kinetic resolution of racemic hydroperoxides can also be achieved by chloroperoxidase (CPO) or Coprinus peroxidase (CiP) catalyzed enantioselective sulfoxidation of prochiral sulfides 22 with a racemic mixmre of chiral hydroperoxides. In 1992, Wong and coworkers and later Hoft and coworkers in 1995 ° investigated the CPO-catalyzed sulfoxidation with several chiral racemic hydroperoxides while the CiP-catalyzed kinetic resolution of phenylethyl hydroperoxide 16a was reported by Adam and coworkers (equation 13). The results are summarized in Table 4. 

Entry Substrate Solvent log P Conversion (%) by Amano PS Conversion (%) by xero gel ... 

Kind R., Li X., Yuan X., Sobolev S. V., Hanka W., Ramesh S. D., Gu Y. G., and Dziewonski A. M. (2002) Global comparison of SS precursor and Ps conversion data from the upper mantle seismic discontinuities. Eos, Trans., AGU 83(47), Pall Meet. Suppl., Abstract S52C-07. 

Fig. 10. One-dimensional phasing depth images for southern Africa, organized by geological province. The munber of events included in the stack and the station name are shown to the right of each trace. The dominant signal on most of the depth images shown is the Ps conversions from the Moho. Relatively thin (35-40 km) crust and sharp, well-defined Ps Moho conversions are associated with undisturbed craton. Ps arrivals associated with modified regions of the craton and post-Archaean terranes tend to be more diffuse and of smaller amplitude (from Nguuri et al. 2001, published in GRL28, 2001, fig,. 2).

Thus, complete ideality [in the sense of (8.33) and (8.35)] does not imply lack of PS. Conversely, lack of PS (in the sense of GAs = GBs) does not imply ideality. We shall further discuss this point in relation to PS in two-component systems in the next section. 

Fig. 5. Diastereomers used in the stereochemical studies on PN to PS conversion. , O. From Ref. 27.

S. Xia, K. Makinwa, S. Nihtianov, A capacitance-to-digital converter for displacement sensing with 17b resolution and 20 ps conversion time, in Sohd-State Circuits Conference Digest of Technical Papers (ISSCC), 2012 IEEE International, 2012, pp. 198-200. 

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