First Synthesis of Free Cholesterol−BODIPY Conjugates
摘要:
Analogues of cholesterol (compounds I and 2) and coprostanol (compound 3) containing the BODIPY fluorophore in the aliphatic tail of the free sterol have been synthesized starting with bisnorcholenic acid, choleric acid 3 beta-acetate, and lithocholic acid, respectively. An ester linkage joining the fluorophore to the sterol nucleus interfered with the ability of the fluorescent sterol to pack with phospholipids in monolayers. However, an analogue in which the linker was devoid of polar atoms exhibited a substantially similar physical behavior to cholesterol in model membranes with respect to localization in raft domains.
An electron-deficient amide is utilized as a directing group to functionalize nonactivated C(sp(3))-H bonds through radical 1,5-hydrogen abstraction. The gamma-bromoamides formed are subsequently converted to gamma-lactones under mild conditions. The method described is not limited to tertiary and secondary positions but also allows functionalization of primary nonactivated sp(3)-hybridized positions in a one-pot sequence. In addition, the broad functional group tolerance renders this method suitable for the late-stage introduction of gamma-lactones into complex carbon frameworks.
Reindel; Niederlaender, Chemische Berichte, 1935, vol. 68, p. 1243,1245