Oral Delivery of Propofol with Methoxymethylphosphonic Acid as the Delivery Vehicle.

Phosphonamidate 3a of methoxymethylphosphonic acid (MMPA) with propofol (1) and l-alanine ethyl ester was found to be an efficient scaffold for the oral delivery of compound 1. The synthesis and evaluation of MMPA based phosphonamidates of compound 1, HSK3486 (2), and other phenolic drugs revealed the general application of MMPA as the effective delivery vehicle for phenolic drugs. On the basis of plasma concentrations of compound 1 and SN38 (14), the oral bioavailability of compound 3a and 15 in beagle dogs was found to be 97.6% and 34.1%, respectively.

CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonding: effect of local rigidification on solvent extraction toward f-block elements.

To understand intramolecular hydrogen bonding in effecting liquid-liquid extraction behavior of CMPO-calixarenes, three CMPO-modified calix[4]arenes (CMPO-CA) 5a-5c with hydrogen-bonded spacer were designed and synthesized. The impact of spacer rotation that is hindered by introduction of intramolecular hydrogen bonding upon extraction of La(3+), Eu(3+), Yb(3+), Th(4+), and UO2(2+) has been examined. The results show that 5b and 5c containing only one hydrogen bond with a less hindered rotation spacer extract La(3+) more efficiently than 5a containing two hydrogen bonds with a more hindered rotation spacer, demonstrating the importance of local rigidification of spacer in the design of extractants in influencing the coordination environment. The large difference in extractability between La(3+) and Yb(3+) (or Eu(3+)) by 5b (or 5c), and the small difference by 5a, suggests intramolecular hydrogen bonding do exert pronounced influence upon selective extraction of light and heavy lanthanides. Log-log plot analysis indicates a 1:1, 2:1 and 1:1 stoichiometry (ligand/metal) for the extracted complex formed between 5b and La(3+), Th(4+), UO2(2+), respectively. Additionally, their corresponding acyclic analogs 7a-7c exhibit negligible extraction toward these metal ions. These results reveal the possibility of selective extraction via tuning local chelating surroundings of CMPO-CA by aid of intramolecular hydrogen bonding.

Alternative strategy for adjusting the association specificity of hydrogen-bonded duplexes.

A strategy for creating new association specificity of hydrogen-bonded duplexes by varying the spacings between neighboring hydrogen bonds is described. Incorporation of naphthalene-based residues has provided oligoamide strands that pair into duplexes sharing the same H-bonding sequences (e.g., DDAA) but differing in the spacings between their intermolecular hydrogen bonds, leading to homo- or heteroduplexes. The ability to manipulate association-specificity as demonstrated by this work may be extended to other multiple hydrogen bonded systems, thereby further enhancing the diversity of multiple hydrogen-bonded association units for constructing supramolecular structures.