Synthesis and LTB4 receptor antagonist activities of the naturally occurring LTB4 receptor antagonist leucettamine A and related analogs
摘要:
The isolation and structure determination of the naturally occurring LTB4 receptor antagonist Leucettamine A (1) was recently reported.1 Herein we describe the synthesis of this natural product, the preparation of several analogues, and their effectiveness as antagonists of [H-3]LTB4 binding to intact human U-937 cells. Total synthesis of Leucettamine A 1) is achieved by a convergent route which takes advantage of the elements of symmetry within the molecule. Syntheses of analogues of 1, which lacked the same degree of symmetry, are achieved by a different approach starting from alpha-amino acids. The natural product 1 inhibits [H-3]LTB4 binding to its receptors on intact human U-937 cells with a K(i) = 3.5 +/- 0. 8 muM and is devoid of measurable agonist activity at the concentrations tested. 2-Amino imidazole analogues of 1 lacking the dioxolane groups were prepared. Generally these are significantly less potent than 1. However, one (26), designed on the basis of a putative structural overlay with LTB4, demonstrated potency comparable to that of the natural product (K(i) = 2.4 +/- 0.2 muM).
Synthesis and LTB4 receptor antagonist activities of the naturally occurring LTB4 receptor antagonist leucettamine A and related analogs
摘要:
The isolation and structure determination of the naturally occurring LTB4 receptor antagonist Leucettamine A (1) was recently reported.1 Herein we describe the synthesis of this natural product, the preparation of several analogues, and their effectiveness as antagonists of [H-3]LTB4 binding to intact human U-937 cells. Total synthesis of Leucettamine A 1) is achieved by a convergent route which takes advantage of the elements of symmetry within the molecule. Syntheses of analogues of 1, which lacked the same degree of symmetry, are achieved by a different approach starting from alpha-amino acids. The natural product 1 inhibits [H-3]LTB4 binding to its receptors on intact human U-937 cells with a K(i) = 3.5 +/- 0. 8 muM and is devoid of measurable agonist activity at the concentrations tested. 2-Amino imidazole analogues of 1 lacking the dioxolane groups were prepared. Generally these are significantly less potent than 1. However, one (26), designed on the basis of a putative structural overlay with LTB4, demonstrated potency comparable to that of the natural product (K(i) = 2.4 +/- 0.2 muM).
We disclose a unprecedented riboflavin promoted Nefreaction of primary nitroalkanes coupled with a nitroaldol reaction. This tandem process allows the synthesis of functionalized nitro alcohols under mild reaction conditions. Secondary nitroalkanes fail to give the expected nitroaldol products although they are consumed under the reaction conditions.