@article{121b299d6a6d46f09ba9191de87a97ad,
title = "(R)-Metacycloprodigiosin-HCl: Chiroptical properties and structure",
abstract = "(R)-Metacycloprodigiosin can exist in three different tautomeric forms, each with hydrogens at C9′ and C12 in syn or anti orientation. With the addition of HCl, this structural diversity reduces to syn-(R)-metacycloprodigiosin-HCl (1a) and anti-(R)-metacycloprodigiosin-HCl (1b), each with multiple conformers. Energetics and chiroptical properties, namely, electronic circular dichroism (ECD) and specific optical rotation (SOR), of (R)-metacycloprodigiosin-HCl have been investigated at B3LYP/6-311++G(2d,2p) level. The experimental ECD spectra of (R)-metacycloprodigiosin-HCl have also been measured. Calculations indicated that the lowest energy conformer of 1b is approximately 2.7 kcal/mol lower in energy than that of 1a, and the energy barrier for anti to syn conversion is approximately 13 kcal/mol. The population weighted calculated SORs of 1a and 1b are, respectively, positive and negative. The respective calculated ECD spectra of these pseudoenantiomers show an almost mirror image relationship between them. The experimental SOR and ECD compare well with those predicted for 1b. Thus, 1b is expected to be predominant, a situation confirmed also by nuclear Overhauser effect (NOE) data, with a similar conclusion reached for prodigiosin R1.",
keywords = "conformers, ECD, energy barrier, ORD, prodigiosins, pseudoenantioisomerism",
author = "Daniela Peixoto and Ferreira, {Elisabete P.} and Louren{\c c}o, {Ana M.} and Johnson, {Jordan L.} and Lobo, {Ana M.} and Polavarapu, {Prasad L.}",
note = "Funda{\c c}{\~a}o para a Ci{\^e}ncia e a Tecnologia, Grant/Award Numbers: UID/QUI/50006/ 2013 and UID/Multi/04378/2013; National Science Foundation, Grant/Award Num ber: CHE1464874; ERDF, Grant/Award Numbers: POCI‐01‐0145‐FEDER–007265 and POCI‐01‐0145‐FEDER–007728 We are very thankful for a sample of natural metacycloprodigiosin obtained from Professor Kevin A. Reynolds and Dr Papireddy Kancharla (Portland State University, Oregon, USA) and Professor R. J. Thomson (Northwestern University, Illinois, USA) for sending us information on the ECD spectrum of synthetic chiral prodigiosin R1, as well as the complete published Supporting Information file. We also thank Professor Y. Hayakawa (Japan) for sending us information on his publications related to metacycloprodigiosin and prodigiosin R1. We thank Dr Jim Cheeseman for helpful communications on transition state calculations. This work was supported by REQUIMTE/LAQV and REQUIMTE/UCIBIO, through Portuguese national funds from Funda{\c c}{\~a}o para a Ci{\^e}ncia e a Tecnologia (FC&T, Portugal)/MEC (UID/ Multi/04378/2013 and UID/QUI/50006/2013, respectively) and cofinanced by the ERDF under the PT2020 Partnership Agreement, POCI‐01‐0145‐FEDER–007728 and POCI‐01‐0145‐FEDER–007265, respectively. The work carried out at Vanderbilt University was supported by NSF (CHE1464874).",
year = "2018",
month = jul,
day = "1",
doi = "10.1002/chir.22867",
language = "English",
volume = "30",
pages = "932--942",
journal = "Chirality",
issn = "0899-0042",
publisher = "Wiley-Liss Inc.",
number = "7",
}