Condensates quartetting

One of the most amazing phenomena in quantum many-particle systems is the formation of quantum condensates. Of particular interest are strongly coupled fermion systems where bound states arise. In the low-density limit, where even-number fermionic bound states can be considered as bosons, Bose-Einstein condensation is expected to occur at low temperatures. The solution of Eq. (6) with = 2/j, gives the onset of pairing, the solution of Eq. (7) with EinP = 4/i the onset of quartetting in (symmetric) nuclear matter. At present, condensates are investigated in systems where the cross-over from Bardeen-Cooper-Schrieffer (BCS) pairing to Bose-Einstein condensation (BEC) can be observed, see [11,12], In these papers, a two-particle state is treated in an uncorrelated medium. Some attempts have been made to include the interaction between correlated states, see [7,13]. 

Compound ii S -LVIII was synthesized by the Ullmann condensation of (— )-6 -bromolaudanosine (XL) with isocorydine (LVI) and was reported to be identical with thalicarpine. However, scrutiny of the spectral properties of thalicarpine showed that they are incompatible with structure i S-LVIII (32). For example, there is no AB quartet in the aromatic proton region of the NMR-spectrum of the alkaloid as would be expected of the neighboring aromatic protons in structure i (S-LVIII. Accordingly the condensation of compounds XL and LVI was reexamined and, as expected, the earlier result was not reproduced. 

Figure 36 (a) Reversible decoration of guanosine hydrazide 1 and of its G-quartet assembly Q1 by condensation with various aldehydes (2-8) (b) Generation of a dynamic library of acylhydrazones C, D and of the acylhydrazone G-quartets A and B from hydrazides 1, 9 and aldehydes 6 and 8. (Reproduced from Ref. 113. National Academy of Sciences, 2005.)... 

The stereochemistry of the related calix[4]resorcinarenes is, for the parent compounds derived from condensation of resorcinols with formaldehyde, similar to the calix[4]arenes. In the NMR spectra the bridging methylene groups show up as an AB quartet at low temperature which coalesces at higher temperatures. When they are obtained from higher aldehydes, the stereochemical outcome of the reaction is much more complex. The conformation of the macrocyclic ring can adopt five extreme conformations, the crown, boat, chair, diamond, and saddle. The... 

H NMR multiple centered at 3.90ppm after 12 min and 90 min of the initial acid-catalyzed hydrolysis of TEOS (r = 1). The complex spectrum obtained after 90 min is a superposition of many quartets resulting from the hydrolysis and condensation products [59]. 

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