Jacobsen structure

A catalytic enantio- and diastereoselective dihydroxylation procedure without the assistance of a directing functional group (like the allylic alcohol group in the Sharpless epox-idation) has also been developed by K.B. Sharpless (E.N. Jacobsen, 1988 H.-L. Kwong, 1990 B.M. Kim, 1990 H. Waldmann, 1992). It uses osmium tetroxide as a catalytic oxidant (as little as 20 ppm to date) and two readily available cinchona alkaloid diastereomeis, namely the 4-chlorobenzoate esters or bulky aryl ethers of dihydroquinine and dihydroquinidine (cf. p. 290% as stereosteering reagents (structures of the Os complexes see R.M. Pearlstein, 1990). The transformation lacks the high asymmetric inductions of the Sharpless epoxidation, but it is broadly applicable and insensitive to air and water. Further improvements are to be expected. 

Jacobsen, T. Airflow and remperature distribution in rooms with displacement ventilation. Ph.D. thesis. Dept, of Building Technology and Structural Engineering, Aalborg University, Aalborg, 1993. 

The Jacobsen-Katsuki epoxidation reaction is an efficient and highly selective method for the preparation of a wide variety of structurally and electronically diverse chiral epoxides from olefins. The reaction involves the use of a catalytic amount of a chiral Mn(III)salen complex 1 (salen refers to ligands composed of the N,N -ethylenebis(salicylideneaminato) core), a stoichiometric amount of a terminal oxidant, and the substrate olefin 2 in the appropriate solvent (Scheme 1.4.1). The reaction protocol is straightforward and does not require any special handling techniques. 

To date, a wide variety of structurally different chiral Mn(III)salen complexes have been prepared, of which only a handful have emerged as synthetically useful catalysts. By far the most widely used Mn(III)salen catalyst is the commercially available Jacobsen catalyst wherein R= -C4H8- and R = = i-Bu (Scheme 1.4.1). In... 

The Jacobsen-Katsuki epoxidation reaction has been widely used for the preparation of a variety of structurally diverse complex molecules by both academia and the pharmaceutical industry. Summarized below are a few examples. 

Study [23] Jacobsen s complex was entrapped in the final step of the zeohte synthesis (method C). This process was possible because MCM-22 zeohte is prepared by condensation of a layered precursor, which is exchangeable by the catalytic complex. Leaching of Mn was not observed in these systems, which is not unexpected bearing in mind that the complex is also bovmd to the zeolite structure through an electrostatic interaction. 

New organocatalysts prepared by the Jacobsen group showed that alkylation of the final amide bond increased the enantioselection (Scheme 38, compare R2 = Me, 98% ee to R2 = H, 91% ee). Thus, the reaction performed with N-allyl benzaldimine and with the dimethylamide-ending thiourea (Scheme 38 with Ri = R2 = Me) gave up to 99% ee. This compound is a structural analogue of the urea depicted in Scheme 36 [148,152,154]. 

Similar organocatalytic species to those successfully used for the Strecker reaction were used for the asymmetric Mannich reaction. Catalyst structure/ enantioselectivity profiles for the asymmetric Strecker and Mannich reactions were compared by the Jacobsen group [160]. The efficient thiourea... 

The ratio of the two forms depends on the cation as well as on a. Ba has a greater tendency to make linkages of the COO-Me-OOC type than Mg and this difference is accentuated when the density of COO" in the polyanion is low. Thus, at a = 025 more Ba ions are in the COO-Ba-OOC form than in the COO-Ba form, while the reverse is true for Mg ions. Moreover, the structure COO-Mg is more stable and soluble than COO-Ba because Mg is more hydrophilic than Ba. For these reasons, Ba is precipitated at a = 0-25 while Mg is not. This interpretation is supported by titration experiments in the presence of divalent cations (Jacobsen, 1962). Magnesium forms very stable hydrates and would be expected to be more difficult to desolvate. 

Bohacek RS, Dalgarmo DC, Hatada M, Jacobsen VA, Lynch BA, MacekKJ, Merry T, Metcalf CA III, Narula SS, Sawyer TK, Shakespeare WC, Violette SM, Weigele M. X-ray structure of citrate bound to Src SH2 leads to a high affinity, bone-targeted Src SH2 inhibitor. J Med Chem 2001 44 660-663. 

Stockman BJ, Waldon DJ, Gates JA, Schaill TA, Kloosterman DA, Mizsak SA, Jacobsen EJ, Belonga KL, Mitchell MA, Mao B, Petke JD, Goodman L, Powers EA, Ledbetter SR, Kaytes PS, Yogeli G, Marshall VP, Petzold GL, Poorman RA. Solution structure of stromelysin complexed to thiadiazole inhibitors. Prot Sci 1998 7 2281-2286. 

GMBS or sulfo-GMBS have been used for studying carnitine palmitoyltransferase-1 in its formation of a complex within the outer mitochondrial membrane (Faye et al., 2007), for investigating protein organization of the postsynaptic density (Liu et al., 2006), and in studying the structure and dynamics of rhodopsin (Jacobsen et al., 2006). 

Fujii, N., Jacobsen, R.B., Wood, N.L., Schoenigeg J.S., and Guy, R.K. (2004) A novel protein crosslinking reagent for the determination of moderate resolution protein structures by mass spectrometry (MS3-D). Bioorg. Med. Chem. Lett. 14, 427-429. 

Jacobsen, R.B., Sale, K.L., Ayson, M.J., Novak, P., Hong, J., Lane, P., Wood, N.L., Kruppa, G.H., Young, M.M., and Schoeniger, J.S. (2006) Structure and dynamics of dark-state bovine rhodopsin revealed by chemical cross-linking and high-resolution mass spectrometry. Protein Sci. 15, 1303-1317. 

Pilot sewer studies are often carried out in systems operating with recirculation. Specific care must be taken in systems where water-gas exchange processes form a part of the mass balance. Critical points are pumps and bends that may change the flow regime, air-water exchange processes, biofilm and particle structure. Figure 7.2 is a sketch of a pilot sewer used for sewer process studies (Tanaka and Hvitved-Jacobsen, 2000). 

Figure 11. X-ray crystal structure of Jacobsen s diimine-copper styrene complex (116) showing aromatic face-face and edge-face interactions (PF6 counterion and some hydrogen atoms omitted for clarity). [Adapted from (62).]...

Jacobsen, Panek and co-workers (86) investigated the intermolecular Si-H bond insertion of diazoesters. Bis(oxazolines) and diimines were found to be effective in this reaction, with diimine enf-88a providing optimal selectivities. As expected, enantioselectivity is a function of silane structure, with bulkier silanes providing higher selectivities but lower reactivity. Both CuOTf and Cu(OTf)2 catalyze this reaction but the Cu(II) precursors leads to much lower enantioselectivity (44% vs 83% at -40°C). 

The Pictet-Spengler reaction is the method of choice for the preparation of tetrahydro-P-carbolines, which represent structural elements of several natural products such as biologically active alkaloids. It proceeds via a condensation of a carbonyl compound with a tryptamine followed by a Friedel-Crafts-type cyclization. In 2004, Jacobsen et al. reported the first catalytic asymmetric variant [25]. This acyl-Pictet-Spengler reaction involves an N-acyliminium ion as intermediate and is promoted by a chiral thiourea (general Brpnsted acid catalysis). 

J. P. Pouquet, Structural Instabilities E. M. Conwell, Transport Properties C. S. Jacobsen, Optical Properties... 

The Jacobsen group introduced the term Schiff base catalyst [122] to demonstrate that the structure of this novel catalyst class originates from Schiff base ligands and incorporates a Schiff base moiety notably, this term does not indicate that these catalysts operate as bases, but their high... 

On the basis of the core structure of catalyst 11 (Figure 6.14), the Jacobsen group constructed a new optimization parallel library of 70 Schiff base compounds incorporating seven amino acids with bulky a-substituents and 10 new salicylal-dehyde derivatives [196]. Each library member was evaluated for enantioselectivity... 

Figure 6.14 The key units of Jacobsen s Schiff base (thio)urea organocatalysts offering access to various structural modifications.

Wenzel and Jacobsen, in 2002, identified Schiff base thiourea derivative 48 as catalyst for the asymmetric Mannich addition [72] of tert-butyldimethylsilyl ketene acetals to N-Boc-protected (hetero)aromatic aldimines (Scheme 6.49) [201]. The optimized structure of 48 was found through the construction of a small, parallel... 

In 2004, Taylor and Jacobsen suggested a procedure for the enantioselective acetyl-Pictet-Spengler reaction, that is the cyclization of electron-rich aryl or heteroaryl groups onto N-acyliminium ion enabling access to substituted tetrahydro-P-carbolines and tetrahydroisoquinolines that are core structure elements in natural and synthetic organic compounds [202, 203]. Screening various thiourea catalyst candidates such as 47 in the formation of model product Np-acetyl-... 

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