Synthesis and preliminary biological evaluation at the glycineB site of (+)- and (-)-3-oxetanylglycine, novel non-proteinogenic amino acids

Unexpected Isomerization of Oxetane-Carboxylic Acids

Many oxetane-carboxylic acids were found to be unstable. They easily isomerized into new (hetero)cyclic lactones while being stored at room temperature or slightly heated. Chemists should keep in mind the high instability of these molecules, as this could dramatically affect the reaction yields and lead to negative results (especially in those reactions that require heating).

Improving the metabolic stability of antifungal compounds based on a scaffold hopping strategy: Design, synthesis, and structure-activity relationship studies of dihydrooxazole derivatives

l-amino alcohol derivatives exhibited high antifungal activity, but the metabolic stability of human liver microsomes in vitro was poor, and the half-life of optimal compound 5 was less than 5 min. To improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of antifungal compounds with a dihydrooxazole scaffold was designed and synthesized. Compounds A33-A38 substituted with 4-phenyl group on dihydrooxazole ring exhibited excellent antifungal activities against C. albicans, C. tropicalis and C. krusei, with MIC values in the range of 0.03-0.25 μg/mL. In addition, the metabolic stability of compounds A33 and A34 in human liver microsomes in vitro was improved significantly, with the half-life greater than 145 min and the half-life of 59.1 min, respectively. Moreover, pharmacokinetic studies in SD rats showed that A33 exhibited favourable pharmacokinetic properties, with a bioavailability of 77.69%, and half-life (intravenous administration) of 9.35 h, indicating that A33 is worthy of further study.

Design and synthesis of novel P2 substituents in diol-based HIV protease inhibitors

The synthesis and SAR of HIV-1 protease inhibitors containing novel P2 structural elements are presented. The inhibitors were designed having hydrogen bond accepting P2 substituents to probe potential favorable interactions to Asp-29/Asp-30 of the HIV-1 protease backbone utilizing inhibitor 3 as a model template. Several inhibitors were synthesized from an L-Val methyl amide P2 motif by appending hydrogen bonding moieties from either the isopropyl side-chain or from the methyl amide portion. The most promising inhibitors 4a and 4e displayed Ki values of 1.0 nM and 0.7 nM respectively and EC50 values in the MT4 cell-based assay of 0.17 microM and 0.33 microM respectively, a slight loss in potency compared to lead inhibitor 3. These inhibitors were also tested against an HIV protease inhibitor resistant strain carrying the M46I, V82F, and I84V mutations. Inhibitors 4a and 4e displayed a 3 and 4 fold change respectively compared with HIV wild type, whereas lead inhibitor 3 showed a higher 9 fold change. This study further demonstrate the chemical tractability of the approach where various P2 substituents can be introduced in just one chemical step from lactone 21 enabling facile modifications of the overall properties in this inhibitor class.

Solid-phase total synthesis of (-)-Phenylhistine and (-)-Aurantiamine. Synthesis of a diverse dehydro-2,5-diketopiperazine library. Part II

The preparation of solid supported glycine phosphonate and its utilization for the total synthesis of two natural products is presented. The proposed protocol combines diversity with accessibility and speed, which makes this scaffold suitable for automated parallel synthesis and combinatorial chemistry. The preparation of a small library of dehydro-2,5-diketopiperazines, combining several natural amino acids with diverse heterocycles (including thiazoles, pyridines, indoles and imidazoles), is also demonstrated.