Synthesis, characterization and absolute configurations of methyl ladderanoates. Issue 1 (11th November 2022)

• Record Type: Journal Article
• Authors: Harris, Constance M.; Harris, Thomas M.; Stec, Donald F.; Schley, Nathan D.; Johnson, Jordan L.; Covington, Cody L.; Polavarapu, Prasad L.
• Is Part Of: Chirality. Volume 35:Issue 1(2023)
• Page Start: 49
• Page End: 57
• Publication Date: 2022-11-11
• Subjects: methyl [3]‐ladderanoate -- methyl [5]‐ladderanoate -- quantum chemical predictions -- specific rotation -- vibrational circular dichroism; Chirality -- Periodicals; Pharmaceutical chemistry -- Periodicals; 541.22
• DOI: 10.1002/chir.23515
• Languages: English
• ISSNs: 0899-0042

Abstract

Abstract: Methyl esters of [5]‐ladderanoic acid and [3]‐ladderanoic acid were prepared by esterification of the acids isolated from biomass at a wastewater treatment plant. Optical rotations at six different wavelengths (633, 589, 546, 436, 405 and 365 nm) and vibrational circular dichroism (VCD) spectra in the 1800–900 cm −1 region were measured in CDCl3 solvent and compared with quantum chemical (QC) predictions using B3LYP functional and 6‐311++G(2d, 2p) basis set with polarizing continuum model representing the solvent. QC predictions gave negative optical rotations at all six wavelengths for ( R )‐methyl [5]‐ladderanoate and positive optical rotations for ( R )‐methyl [3]‐ladderanoate, the same signs as previously reported for the corresponding acids. The crystal structure of (−)‐methyl [5]‐ladderanoate independently confirmed ( R ) configuration. The QC‐predicted VCD spectra using Boltzmann population weighted spectra of individual conformers did not provide satisfactory quantitative agreement with the experimental VCD spectra. An improved quantitative agreement for VCD spectra could be obtained when conformer populations were optimized to maximize the similarity between experimental and predicted VCD spectra, but more improvements in VCD predictions are needed. Abstract : The mixture of [5]‐ and [3]‐ladderanoic acids, isolated from the biomass in a waste water treatment plant has been successfully converted to corresponding mixture of methyl esters and then individual esters separated and characterized. The absolute configurations of methyl [5]‐ and [3]‐ladderanoates have been determined, as (−)‐( R ) and (+)‐( R ), respectively.