Noyori procedure

The Noyori procedure was applied to a total synthesis of baiyunoside, a sweet principle, using 2,3,4-tri-<9-benzyl-D-xylopyranosyl fluoride (18 see Table 1), and a synthesis of glycotriosyl ceramide. A model experiment for the synthesis, using 18, showed a solvent dependence for the a ratio of the products. In this case, the use of acetonitrile, oxolane, or ether gave the a anomer (1,2-a.v), and the use of toluene or hexane gave the P anomer (1,2-trans), preponderantly. 

After extensive developmental studies, [35] the final crucial element in our most recent synthesis of epothilone B involves an asymmetric catalytic reduction of the C3 ketone of 67 proceeding via a modified Noyori procedure (Scheme 2.8, 67—>68). In the event, Noyori reduction of ketone 67 afforded the desired diol 68 with excellent diasteresdectivity (>95 5). The ability to successftdly control the desired C3 stereochemistry of the late stage intermediate 68 permitted us to introduce the Cl-C7 fragment into the synthesis as an achiral building block. 

A pilot process was developed for an intermediate of the NMDA 2B receptor antagonist Ro 67-8867, involving the hydrogenation/dynamic kinetic resolution of a cyclic a-amino ketone using an optimized Noyori procedure with a MeO-biphep ligand (69). The Ru-catalyzed reaction was carried out on a 9-kg scale with excellent enantio- and diastereo-selectivities and very high TON and TOF. 

Takaya, H. Ohta, T. Inoue, S. Tokunaga, M. Kitamura, M. Noyori, R. Org. Synth, procedure 2578 being checked. 

The standard work of Evans [2] as well as a survey of the papers produced in the Journal of Labeled Compounds and Radiopharmaceuticals over the last 20 years shows that the main tritiation routes are as given in Tab. 13.1. One can immediately see that unlike most 14C-labeling routes they consist of one step and frequently involve a catalyst, which can be either homogeneous or heterogeneous. One should therefore be able to exploit the tremendous developments that have been made in catalysis in recent years to benefit tritiation procedures. Chirally catalyzed hydrogenation reactions (Knowles and Noyori were recently awarded the Nobel prize for chemistry for their work in this area, sharing it with Sharpless for his work on the equivalent oxidation reactions) immediately come to mind. Already optically active compounds such as tritiated 1-alanine, 1-tyrosine, 1-dopa, etc. have been prepared in this way. 

Related catalytic enantioselective processes It is worthy of note that the powerful Ti-catalyzed asymmetric epoxidation procedure of Sharpless [27] is often used in the preparation of optically pure acyclic allylic alcohols through the catalytic kinetic resolution of easily accessible racemic mixtures [28]. When the catalytic epoxidation is applied to cyclic allylic substrates, reaction rates are retarded and lower levels of enantioselectivity are observed. Ru-catalyzed asymmetric hydrogenation has been employed by Noyori to effect the resolution of five- and six-membered allylic carbinols [29] in this instance, as with the Ti-catalyzed procedure, the presence of an unprotected hydroxyl function is required. Perhaps the most efficient general procedure for the enantioselective synthesis of this class of cyclic allylic ethers is that recently developed by Trost and co-workers, involving Pd-catalyzed asymmetric additions of alkoxides to allylic esters [30]. 

From the point of view of efficiency and application to the industrial production of optically pure compounds the chiral catalyst procedure is the methodology of choice. In this context. Sharpless asymmetric epoxidation and dihydroxylation, Noyori-Takaya s second generation asymmetric hydrogenations and Jacobsen s epoxidation [3] have had a tremendous impact in the last few years and they constitute the basis of the newly spawned "chirotechnology" firms, as well as of the pharmaceutical, fine chemical and agriculture industries. 

The procedure described is based on the selective reduction with diimide described by Ohno and Okamoto and by Nozaki and Noyori. It illustrates the generation of diimide from the air oxidation of hydrazine and the use of diimide for the selective reduction of the trans double bond in cis,trans,trans-, S,9-cyc o-dodecatriene, the product of trimerization of butadiene. ... 

BrXuPHOS (1) may be prepared (Figure 3.4) from bis(dimethylamino)phos-phine (2), the preparation of which has been described in a previous volume in this series,in a condensation with BINOL (3). The preparation procedure for the ruthenium(II) complex (S, S, 55)-BrXuPHOS-Ru-DPEN (4) is a modification of that reported by Noyori. All reactions described below must be carried out under an inert atmosphere of argon or nitrogen. Examples of ketone reductions using (4) as the catalyst are given in Figure 3.5 and Table 3.5. 

Preparation of the Aldehyde 2 The absolute configuration of the iriene aldehyde 2 was set by Noyori hydrogenation of ethyl butyrylacetate S. Silylation and Dibal reduction then gave the aldehyde 6. Reduction of the homologated ester gave the alcohol, which was oxidized to the desired aldehyde 7 by the Swem procedure. Condensation of 7 with the Wollenberg stannyl diene followed by deprotection then gave the unstable aldehyde 2. 

Suzuki, M. Morita, Y. Koyano, H. Koga, M. Noyori, R. Three-Component Coupling Synthesis of Prostaglandins. A Simplified, General Procedure, Tetrahedron 1990,46,4809. 

The mixture of 40a and 40b was directly converted to the corresponding acetonide 41 (Scheme 8). Then, the asymmetric transfer hydrogenation was performed following Noyori s procedure.28 The... 

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