Unlike H and 13 C with a 'nuclear spin' I = ½, both naturally occurring isotopes of boron i.e. B (I = 3) and B (I = 5/2) are NMR active; however, the latter is more versatile than the erstwhile for NMR investigations by virtue of the fact that B has a natural abundance of only 19.6%, whereas B exhibits a natural abundance of 80.4%, as such B comes with a much lower receptivity i.e. receiver gain, and quadrupole moment almost thrice as much as that for B, which broadens 10 B NMR signals. Moreover, the Larmor frequency of B is almost three times lower than that for B, resulting in a much lower signal resolution and coupling constants i.e. J (in Hz) in 10 B NMR spectra. Despite these drawbacks B NMR can be particularly useful in niche mechanistic studies such as rearrangements. NMR spectroscopy much to contemporary efforts has proved exceptionally advantageous in elucidating structures of boron compounds, and their behaviour in solutions. The extrapolation of NMR activities of other common NMR active nuclei such as 1 H, 13 C, 15 N, 31 P etc., to B NMR suggests that the following factors should determine chemical shifts (δ) in B NMR spectra: However, the above is found not to be true for many B NMR spectra. For example, the signals from B 1 and B 2 in the 11 B NMR spectrum of n-B 9 H 15 are ~ 64.7 ppm apart, such that B 2 resonates at the highest field and B 1 at the lowest field in the aforementioned B NMR spectrum, in spite of both B 1 and B 2 in n-B 9 H 15 exhibiting identical connectivity, hybridisation and even immediate bonding environment (Fig. ). On the other hand, in stark contrast to other NMR active nuclei, electron density does not appear to preponderate over other factors in determining the position of chemical shifts in B NMR spectra, as the boron atoms of higher electron density in B 7 H 7 2-are less shielded than their counterparts of lower electron density in the same cluster. To this end, there are no hard and fast rules as yet to fully predict or explain some of the anomalies that have been observed for B NMR spectra, and each and every single boron compound can give rise to distinctive and unexpected 11 B NMR spectra, which have been observed for the novel boronate esters herein, and forms the basis of the discussions below. Recent protein-directed dynamic combinatorial chemistry studies of L-cysteine derivatives with 2formylphenylboronic acid (2-FPBA) on the surface i.e. in crystallo of oxacillinases e.g. OXA-10 brought home to us an intriguing quadrivalent cyclic boronate ester i.e. 12 (unpublished) (Fig. ), given that the same observed 'tetracyclic caged' structure for 12 has been reported in solution elsewhere, it is conceivable that based on the observed spectroscopic and X-ray crystallographic data, boronate esters 11 & 13-18 (Fig. ) should also follow suit. Inasmuch as, both the diazaborines and boronate esters herein presumably, almost certainly feature 'quadrivalent' boron species, a comparison of chemical shifts (vide infra) in B NMR spectra of the thus obtained diazaborines and boronate esters (Fig. ) not only provides structural insight into these intriguing scaffolds, but also paves the way for a better understanding of bonding in such boron species, and salient factors in their B NMR resonance frequencies.