Determination of the absolute configuration of Anisotome irregular diterpenes: application of CD and NMR methods.
Several Anisotome diterpene derivatives were synthesized in an attempt to obtain a crystalline compound for X-ray analysis. Although we were unable to obtain a suitable crystal, the absolute configuration of the irregular diterpene skeleton was determined using two other techniques: a circular dichroism (CD) protocol based on a tetraarylporphyrin molecular tweezer that allowed prediction of the absolute stereochemistry on a microscale level, and a method employing differences in NMR shifts from derivatization of the naturally occurring acid 1 with enantiomers of a phenylglycine methyl ester (PGME) chiral anisotropic reagent. The excellent agreement between the CD and NMR methods led to the assignment of a 2S-absolute configuration for anisotomenoic acid 1.
Van Klink
John W
JW
Crop and Food Research, Department of Chemistry, Otago University, Dunedin, New Zealand. vanklinkj@crop.cri.nz
Baek
Seung-Hwa
SH
Barlow
Anna J
AJ
Ishii
Hideki
H
Nakanishi
Koji
K
Berova
Nina
N
Perry
Nigel B
NB
Weavers
Rex T
RT
D002942:Circular Dichroism; D004224:Diterpenes / Q000737:chemistry*; D005998:Glycine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D019684:Magnoliopsida / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D004224:Diterpenes; C033393:methyl phenylglycine; D005998:Glycine