Practical Method for the Absolute Configuration Assignment of tert/tert 1,2-Diols Using Their Complexes with Mo₂(OAc)₄

Abstract

We describe here an application of the practical, simple, and reliable approach for the determination of the absolute configuration of sterically demanding tert/tert vic-diols. According to this method, it is only necessary to mix dimolybdenum tetraacteate and a chiral diol in DMSO and record the CD spectra in the 250-650 nm spectral range. From the sign of the CD bands occurring at around 310, 350, and 400 nm, it is possible to establish the chirality of the diol unit expressed by the sign of the O-C-C-O torsion angle. Because the preferred conformation of the diol in the formed complex is known, we are able to determine the absolute configuration of the carbon atoms in the diol subunit even in flexible tert/tert vic-diols.

Terpenoid and Phenolic Metabolites from the Fungus Xylaria sp. Associated with Termite Nests

“…(9) 131.0 C (10) 134.4 C(10), and from HÀC(8) to C(1), C(6), and C(10), as well as the molecular formula of 4 established the planar structure as 3,4,5-trihydroxy-1-tetralone. A NOESY correlation of HÀC(3) with HÀC(4), together with the smaller coupling constants between HÀC(3) and HÀC(4) (2.9 Hz) suggested a cis relationship for the 3,4-diol moiety [17], implying that its absolute configuration could be assigned using the in situ dimolybdenum CD method developed by Snatzkes method [18] [19]. Upon addition of dimolybdenum tetraacetate [Mo 2 (OAc) 4 ] to a solution of 4 in DMSO, a metal complex was generated as an auxiliary chromophore.…”

Cyclohexenones and isocoumarins from an endophytic fungus ofSarcosomataceaesp.

“…Thus, the planar structure of 3 was depicted as shown in Figure 1 Thus, the relative configuration of compound 3 was determined as shown in Figure 5. The absolute configuration of the 1,2-diol moiety in 3 was assigned using the in situ dimolybdenum CD method, developed by Snatzke and Frelek [9,10]. The negative cotton effect at around 310 nm observed in the induced CD spectrum permitted the assignment of absolute configuration as 4R, 5R on the basis of the empirical rule proposed by Snatzke.…”

“…Thus, the absolute configuration of 3 was assigned as 4R, 5R, 6R, 2 0 R. Thus, the chemical structure of compound 3 was determined and it was named sarcosone C. Compound 4 was obtained as white amorphous powder. Its molecular formula was established to be C 10 [11], except that the methyl signal of mellein was replaced by a hydroxymethyl group signal in 4. Thus, the planar structure of 4 was determined, which was confirmed by 1 H -1 H COSY and HMBC spectra ( Figure 2).…”

Complementarity of electronic and vibrational circular dichroism based on stereochemical studies of vic-diols

“…Such a defined conformation enables, in turn, determination of the AC of an examined diol based on the ECD spectra alone. The assignment of the AC should be based on the helicity rule correlating a positive/negative sign of the O-C-C-O torsion angle of the vic-diol subunit with the positive/ negative sign of CEs observed respectively in the 280-400 nm spectral range [26,27].…”