Chirality center phosphorus

If we were to assign priorities for the second chirality center, phosphorus will receive the first priority, and hydrogen will receive the fourth priority. Since there are two carbon atoms attached at this chirahty center, we will need a tie breaker for this side as well. The carbon atom that is coimected to the propyl chain is directly attached to C, H, and H while the other carton atom is connected to the O, C, and H. Since oxygen has the highest atomic number, this side will win. For this chirality center, when H is placed on the wedge, and the propyl on a dash, the configuration is R... 

The most common cause of chirality is the presence of four different substituents bonded to a tetrahedral atom, but that atom doesn t necessarily have to be carbon. Nitrogen, phosphorus, and sulfur are all commonly encountered in organic molecules, and all can be chirality centers. We know, for instance, that trivalent nitrogen is tetrahedral, with its lone pair of electrons acting as the fourth "substituent" (Section 1.10). Is trivalent nitrogen chiral Does a compound such as ethylmethylamine exist as a pair of enantiomers ... 

The numerous chiral phosphine ligands which are available to date [21] can be subclassified into three major categories depending on the location of the chiral center ligands presenting axial chirality (e.g., BINAP 1 and MOP 2), those bearing a chiral carbon-backbone (e.g., DIOP 3, DuPHOS 4), and those bearing the chiral center at the phosphorus atom (e. g., DIPAMP 5, BisP 6), as depicted in Fig. 1. 

Phosphorus compounds, 19 19-73 bond properties of, 19 26 chemical properties of, 19 20-31 chiral-centered, 19 25-26 economic aspects of, 19 67-69 as flame retardants, 19 51 inorganic, 11 487-488 oxidation states, coordination numbers, and geometries of, 19 20-26 as oxyacid derivatives, 19 20 reactive organic, 11 496 497 titanium in, 25 56-57 triply connected, 19 25 U.S. prices of, 19 68t U.S. production of, 19 67t... 

After conversion of the phosphonate monoester into a phosphonochloridate, or subsequently to a phosphonamidate, a new chiral center at phosphorus is created. Thus, after coupling to a chiral amine, even optically pure aminoalkylphosphonate monoesters produce a mixture of two diastereomers (racemic aminoalkylphosphonates result in four diastereo-mers). It is often possible to separate these diastereomers chromatographically. Of course, this is not necessary if the phosphorus ester will eventually be hydrolyzed. 

Analytical Properties Resolution of enantiomers such as trans- 1,3-cyclohexene dibenzoate, 3,5-pentylene dibenzoate, 3,5-dichlorobenzoate, triacetylacetonates, and racemic compounds having phosphorus as a chiral center this phase will also resolve achiral compounds Reference 45, 46... 

Most chiral organic compounds have at least one asymmetric carbon atom. Some compounds are chiral because they have another asymmetric atom, such as phosphorus, sulfur, or nitrogen, serving as a chirality center. Some compounds are chiral even though they have no asymmetric atoms at all. In these types of compounds, special characteristics of the molecules shapes lend chirality to the structure. 

The TBP-phosphorus atom with three equivalent ligands can no longer be a chiral center. As a consequence, the positional exchange of ligands in the 1,2-oxaphospholene (64) (Scheme 15) reported a few years... 

There are two basic prerequisites for completing an enzymatic investigation involving substitution at phosphorus. A substrate for the subject enzyme must first be synthesized with a chirally substituted phosphorus at the reaction center. ATP is a concrete example with three potentially chiral phosphorus centers, each of which undergoes enzymatic substitution. The enzymatic bond cleavages resulting from substitution at P0, and Py are illustrated in Fig. 3. Substitution at Pa is catalyzed by nucleotidyltransferases and certain ATP-dependent synthetases, and substitution at Py is catalyzed by phosphotransferases, other ATP-dependent synthetases and... 

These compounds are important in asynunetric catalysis, in which a prochiral substrate is converted into a chiral product. There are basically three types of chiral phosphines. Firstly, there are phosphines of the type PRR R", where the chiral center is the phosphorus atom. Secondly, the substituent(s) or the molecule as a whole may be chiral. Finally, a coordinated phosphine complex may be chiral at the metal center. 

Typical production batches of nerve agents formerly intended for military use are mixtures of enantiomers obtained from nonchiral synthesis (Figure 50.1). Sarin, cyclosarin, tabun, and VX consist of mixtures of two enantiomers each of which differs in the chirality at the central phosphorus atom thus enabling rotation of linearly polarized light clockwise [P(+)-enantiomers] or anticlockwise [P(—)-enantiomers] (Figure 50.1). In contrast, chirality of soman appears more complex based on two chiral centers, which reside at the phosphorus atom, P(-f) and P(—), and additionally in the pinacolyl moiety, C(-f) and C( ). Hence, soman occurs in four stereoisomeric conformations as two pairs of diastereomers P(-E)C(+),... 

In the majority of cases, chirality results from the three dimensional orientation of four different substituents around a carbon atom forming the chiral center. In addition the orientation of atoms or groups around sulfur, phosphorus, and nitrogen atoms can sometimes form a chiral center. Examples of chiral drugs are numerous but include Certirizine (1), Rotigotine (2), and Ifosfamide (3). 

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