Xinglong Jiang

New observations on peptide bond formation using CDMT

Abstract The optimized formation of the peptide bond by means of 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) has been found to occur rapidly and essentially quantitatively in a one-pot, one-step procedure. This new method is effective for the coupling of a variety of reactive partners, including chiral amino acids (e.g. N -acetyl- l -leucine) without significant loss of configuration. Significant racemization was observed when the typical literature conditions were used, due to the formation of an azlactone intermediate which is configurationally unstable under the reaction conditions. A simpler, precipitative workup procedure is also disclosed in this report.

In-situ generation of Et3SiBr from BiBr3 and Et3SiH and its use in preparation of dialkyl ethers

Abstract The reported BiBr 3 –Et 3 SiH catalyzed reductive etherifications of silyl ethers with carbonyl compounds are shown to be catalyzed by the in situ formed Et 3 SiBr and verified by an independent use of the commercial reagent. As Et 3 SiBr is moisture sensitive and is not readily available, this in situ generation is still recommended as the method of choice. Utilizing this method, several alcohols were transformed under very mild conditions into dialkyl ethers via their silyl intermediates, such as TES, TBDMS, and TIPS.

Etherification of alkoxydialkylsilanes with carbonyl compounds

Abstract A novel method for preparing ethers from alkoxydialkylsilanes and carbonyl compounds through reductive etherification is described. The salient feature in this method is the utilization of internal hydrogen as the hydride source for reducing the oxonium intermediate generated by using the Cl(R) 2 SiBr[BiBr 3 /Cl(R) 2 SiH] catalytic system.

Concise Synthesis of JN403, a Novel Nicotinic Acetylcholine Receptor α7 Selective Agonist

Abstract A three-step method for the synthesis of (S)-(1-aza-bicyclo[2.2.2]oct-3-yl)carbamic acid (S)-1-(2-fluorophenyl)ethyl ester HCl salt (12) was developed, starting from alcohol 3 and resulting in an overall yield of 50%. A key feature of the present study is the need to use a strong base such as n-butyllithium for neutralizing the HCl salt of 5 during the condensation of 4 with 5.