Nuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and .alpha.-methoxy-.alpha.-trifluoromethylphenylacetate (MTPA) esters

Abstract

An empirically derived correlation of configuration and nmr chemical shifts for diastereomeric mandelate, O-methylmandelate and a-methoxy-a-trifluoromethylphenylacetate (MTPA) esters has been developed and rationalized in terms of useful models 4 and 5. These models have been successfully applied to well over 40 examples as given in Table I. The correlations involve the relative chemical shifts of the proton resonances from the groups attached to the carbinyl carbon of these diastereomeric esters. This nmr-configurational correlation should prove to be widely applicable in assigning the configuration of additional secondary carbinols, as well as other chiral -substituted carboxylic acid derivatives.(1) We gratefully acknowledge a grant in support of this study by the National Science Foundation (NSF GP 27448).(2) Taken from the Ph.D. thesis of J.

Oxepinochromenones, Furochromenone, and their Putative Precursors from the Endolichenic Fungus Coniochaeta sp.

“…The absolute configuration of 1 was assigned using the modified Mosher method. 22,23 Treatment of 1 with (S)-and (R)-MTPA-Cl afforded the (R)-(1a) and (S)-MTPA (1b) monoesters, respectively. The difference in chemical shift values (∆δ ) δ S -δ R ) for 1b and 1a was calculated to assign the 7S configuration.…”

New antimicrobial compounds from a marine-derived Bacillus sp.

“…The absolute configurations of 1 at selected stereocenters were determined by the modified Mosher's method. 12 10,15 and both 1 and macrolactin A might be produced by a common biosynthetic pathway. 16 So, it might therefore be assumed that the absolute configuration of C-23 in 1 was R, as all the macrolactin family members are produced in same biogenesis and the shared stereocenters between macrolactin A and its derivatives had the same absolute configurations.…”

Synthesis of the C11–C23 Fragment of the Potent Antitumor Agent Dictyostatin

“…The absolute configuration of epoxy alcohol 6 was confirmed by comparison of to value of the optical rotation was determined using the Mosher ester method, as shown in Scheme 1. 11 In addition, we have prepared allylic alcohol 5 by a shorter synthetic route (Scheme 2). 12 Homoallylic alcohol 8 was converted to the corresponding p-methoxybenzyl ether 9 in 80% yield.…”