Formal Synthesis of Belactosin A and Hormaomycin via a Diastereoselective Intramolecular Cyclopropanation of an α-Nitro Diazoester

Abstract

An efficient and convenient methodology for the synthesis of the 3-(trans-2-aminocyclopropyl) alanine and 3-(trans-2-nitrocyclopropyl) alanine moieties found in the core of belactosin A and hormaomycin, respectively, is reported. By using an enantioenriched substituted alpha-nitro diazoester in a diastereoselective intramolecular cyclopropanation reaction, the trans-nitrocyclopropyl alanine moiety can be obtained efficiently in five steps from the initial alpha-nitrocyclopropyl lactone unit, thus achieving the synthesis of the cyclopropane core of the two natural products.

Urea‐Induced Acid Amplification: A New Approach for Metal‐Free Insertion Chemistry

“…We first attempted to trap a potential donor/acceptor carbene intermediate through an intramolecular cyclopropanation of the olefin in the cinnamyl alcohol-derived a-aryldiazoacetate 3 g (Scheme 4 b). [18] When 3 g was subjected to the standard OÀH insertion reaction conditions, we observed only formation of the a-acetoxyester 4 q. Importantly, when acetic acid was omitted from the reaction, under otherwise identical reaction conditions, we observed no reaction after 48 h at 23 8C.…”

Aruncin B: Synthetic Studies, Structural Reassignment and Biological Evaluation

“…Remarkably, MBH reaction of lactone 48 with aldehyde 53 using a MgI 2 /TMEDA complex‐DMAP catalytic system delivered butenolide 54 as an inseparable E ‐/ Z ‐mixture. The concomitant and fortuitous allylic oxidation presumably occured via hydrogen atom abstraction at the bis‐allylic position; this aerobic oxidation was not observed on the 6‐membered ring system, and allylic hydrogen atom abstraction is probably favoured on the 5‐membered ring system by generation of the aromatic oxyfuran radical (show in parenthesis in Scheme ).…”

Time-programmable pH: decarboxylation of nitroacetic acid allows the time-controlled rising of pH to a definite value

“…Nitroacetic acid 1 was prepared as previously described, 21 and alpha-cyclodextrin 6 and p -aminobenzoic acid 7 were purchased from Merck and used as received. pH measurements were carried out with a micro glass electrode 52 08HACH (Ag/AgCl) connected to a Crison pH 25+ pH-meter and the fluorescence measurements were carried out with a Horiba Jobin-Yvon FLUOROMAX 4 spectrofluorometer.…”