Mosher method, absolute configuration

Figure 1-25. Mosher s method for determining the absolute configuration of compound...

Ohtani, I. Kusumi, T. Kashman, Y. Kakisawa, H. (1991) High-field FT NMR applications of Mosher s method. The absolute configuration of marine trap ioids. J. Am. Chem. Soc., 113, 4092-6. 

In addition to identification of flavan-3-ols and derivatives from natural sources (Table 11.3, Figure 11.3-Figure 11.5, Figure 11.7, and Figure 11.8), several synthetic studies and efforts at establishing absolute configuration have been reported. The modified Mosher method has been successfully applied to configurational definition of the flavan-3-ols and 4-arylflavan-3-ols, and the A-type proanthocyanidins. " The first stereoselective synthesis of a series of flavan-3-ol... 

Rossouw, W. et al., Oligomeric flavanoids. Part 17. Absolute configurations of flavan-3-ols and 4-aryIflavan-3-ols via a Mosher s method, Tetrahedron, 50, 12477, 1994. 

Fig. (5). Determination of the absolute configuration of broussonetine N (15) by the Mosher s method.

Four simple sulfates (158-161) were identified as antimicrobial constituents of Halocynthia roretzi from Japan [160]. Sodium (or potassium) 2,6-dimethyIheptyl sulfate (161) was also found in Polycitor adriaticus from Croatia [161]. The absolute configuration of 2,6-dimethylheptyl sulfate (161), which has also been found in other Mediterranean ascidians, has been determined using Mosher s method [162],... 

Yessotoxin (214) is a polyether from the scallop Patinopecten yessoensis and has been implicated in diarrhetic shellfish poisoning (DSP). The structure and partial stereochemistry of yessotoxin were deduced from spectral data [219]. The relative stereochemistry of yessotoxin and the structures of two new analogues, 45-hydroxyyessotoxin (215) and 45,46,47-trinoryessotoxin (216) were also established [220]. The absolute stereochemistry of yessotoxin (214) was determined by NMR spectroscopy using a chiral anisotropic reagent [221]. The absolute configuration at C45 in 45-hydroxyyessotoxin (215), isolated from P. yessoensis, was determined by the use of a modified Mosher s method [222]. 

Ohtani, I., Kusumi, T., Ishitsuka, M. O., and Kasikawa, H. 1989. Absolute configuration of marine diterpenes possessing a xenicane skeleton. An application of an advanced Mosher s method. Tetrahedron Lett. 30, 3147-3150... 

Rezanka analysed the fatty acid composition of several species of myxomycetes. In addition to the common fatty acids, polyunsaturated and methylene non-interrupted polyunsaturated fatty acids, for example, with 5, 9- and/or 5, 11-double bonds, were identified by GS-mass spectrometry of their corresponding oxazolines [25]. Multibranched polyunsaturated fatty acid and its four glycosides (50 -54) were isolated from seven different myxomycetes [26]. The absolute configurations of hydroxyl groups were determined by modified Mosher s method, and the glycosides were revealed to contain glucose, mannose, and rhamnose. It may be interesting that these fatty acid constituents contained by the seven species of myxomycetes were different (Table 1). 

Absolute configuration of C(4) in C(4)-hydroxylated compounds determined by NMR analysis of Mosher ester derivatives and comparison to model compounds. All configurations studied determined to be R at C(4). Method also applicable for determining the relative configuration between C(4) and C(36), as well as the absolute configurations of carbinol centers adjacent to THF rings. 

In another experiment, annonadn (3) was oxidatively cleaved with mCPBA to muricatacin (38) (Figure 21), the absolute configuration of which had been established by optical rotation. This conversion suggested the /7 configuration at C(20) of annonacin. This fact was later borne out by the Mosher ester method described earlier in this chapter, lending support to the validity of the method. 

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