Synthesis of a-halo and a-deuterio--lactams
A convenient synthesis of 3,3-dibromo-2-azetidinones involves the reaction of an imine with the trimethylsilyl ester of tribromoacetic acid and triphenylphosphine; reduction with η-Bu3SnH and ηBu3SnD can be controlled to lead to cis-3-bromo-2-azetidinones, and cis or trans 3-deuterio-2-azetidinones.
The lake sediments have registered the information of palaeoclimate and palaeoenvironment in the lake itself and the regional scale. This also leads to a complexity in study of the palaeolimnology by all kinds of proxies. How to purify these proxies to indicate the palaeoclimate has become a problem to be solved. Most of the proxies can qualitively identify the percentage of allochthonous and autochthonous organic components, e.g. δ13corg CD/TC. The model introduced in this note has provided a method of quantitatively calculating the amount of allochthonous organic carbon. As for determination of regulating parameters, i.e. A1 and As, further work is still in need.