Complete NMR assignment and conformational analysis of 17‐α‐ethinylestradiol by using RDCs obtained in grafted graphene oxide

Abstract

The H and C NMR spectra of 17-α-ethinylestradiol (EE2), a well-known contraceptive, including diastereotopic methylene groups, were fully assigned with the help of residual dipolar couplings (RDC) measured in the recently developed grafted graphene oxide orienting medium. RDC analysis, which included all D couplings and the long-range D H-C≡ C coupling, also pointed to the presence of a minor conformation arising from pseudo-rotation of the steroid B ring. Saturation-transfer difference (STD) measurements revealed that the most likely interaction between EE2 and orienting medium occurred on the C and D ring. Copyright © 2016 John Wiley & Sons, Ltd.

Valine derived poly (acetylenes) as versatile chiral lyotropic liquid crystalline alignment media for RDC‐based structure elucidations

“…Nonetheless, in the last decade, both alternatives have been applied to an ever‐increasing number of structural problems in which configurational problems played a dominant role 1g, 4 . This development was driven by successful work on new media being compatible with organic solvents and the exploitation of polymer classes beyond the homopolypeptides dominating the LLC phases for many years 1v, 3i, k, 5 .…”

Homonuclear decoupling by projection reconstruction

“…The steroid offers several aliphatic and aromatic signals, for which 1 J CH coupling constants can be straightforwardly measured using conventional CLIP‐HSQC spectra as long as spectra have sufficient resolution in the carbon dimension. The CH 2 group at C12, however, displays overlapping signals in the CLIP‐HSQC, which prevents proper coupling extraction (see Figure and Table , with the assignment taken from França et al). We therefore recorded four HR‐HSBC spectra with κ = ±1 and ±10 for homodecoupling via projection reconstruction.…”

Practical considerations for working with graphene oxide as alignment media for RDC measurements

“…Modifying the GO is a promising path to overcome this limitation. [18,19] Modified GO might also facilitate changing the alignment direction and not just the strength of alignment.…”

“…[17] With the proven possibility of modifying the GO sheets to be compatible with even more organic solvents, this alignment media has many exciting unexplored possibilities for becoming the alignment media of choice in future RDC studies. [18,19] There is currently a high threshold towards the use of RDCs in routine analysis by non-specialists. Part of this is due to sample preparation being complicated or at least greatly dependent on/aided by experience.…”