Vanadium Haloperoxidase-Catalyzed Bromination and Cyclization of Terpenes

Abstract

Marine red algae (Rhodophyta) are a rich source of bioactive halogenated natural products, including cyclic terpenes. The biogenesis of certain cyclic halogenated marine natural products is thought to involve marine haloperoxidase enzymes. Evidence is presented that vanadium bromoperoxidase (V-BrPO) isolated and cloned from marine red algae that produce halogenated compounds (e.g., Plocamium cartilagineum, Laurencia pacifica, Corallina officinalis) can catalyze the bromination and cyclization of terpenes and terpene analogues. The V-BrPO-catalyzed reaction with the monoterpene nerol in the presence of bromide ion and hydrogen peroxide produces a monobromo eight-membered cyclic ether similar to laurencin, a brominated C15 acetogenin, from Laurencia glandulifera, along with noncyclic bromohydrin, epoxide, and dibromoproducts; however, reaction of aqueous bromine with nerol produced only noncyclic bromohydrin, epoxide, and dibromoproducts. The V-BrPO-catalyzed reaction with geraniol in the presence of bromide ion and hydrogen peroxide produces two singly brominated six-membered cyclic products, analogous to the ring structures of alpha and beta snyderols, brominated sesquiterpenes from Laurencia, spp., along with noncyclic bromohydrin, epoxide, and dibromoproducts; again, reaction of geraniol with aqueous bromine produces only noncyclic bromohydrin, epoxide, and dibromoproducts. Thus, V-BrPO can direct the electrophilic bromination and cyclization of terpenes.

A study on the electronic effect of para substituents in the aryloxy ring of the hydrazone ligands on the vanadium centre in a family of mixed-ligand [VVO(ONO)(OO)] complexes

“…spectroscopy and was found to be present in a nearly equimolar ratio in CDCl 3 solution. The spectral data of (2A) and (2B) As in the previous cases, the presence of two isomeric forms (3A) and (3B) was also observed for complex (3) and was found to be present in a 3:1 ratio in CDCl 3 solution. Spectral data for (3A) and (3B) are collected in Table 4 …”

“…In vanadium chemistry, two commonly occurring motifs, viz., VO 2+ and VO 3+ , have attracted special attention after the discoveries of their involvements in many biochemical and physiological processes such as haloperoxidation [1][2][3][4], phosphorylation [5], vanadium nitrogenases [6], a-olefin polymerization [7][8][9][10][11], insulin mimicking [12][13][14][15][16][17][18][19][20][21], anticancer [22,23], antitumour [24] and antifungal/antibacterial [25] activities. Due to hard acidic nature of these two motifs, they have strong affinity towards the hard basic O, N-donor ligands.…”

Structural models of vanadate-dependent haloperoxidases, their reactivity, immobilization on polymer support and catalytic activities

“…These enzymes catalyse the oxidation of halides (X − ), by peroxide as oxidant, to hypohalous acid (HOX) which further halogenates hydrocarbons non-enzymatically according to (1) and (2).…”

Oxovanadium(IV)-Salen Ion Catalyzed H2 O2 Oxidation of Tertiary Amines to N -Oxides- Critical Role of Acetate Ion as External Axial Ligand

“…(1) and (2). Based on the Michaelis-Menten formulation the observed rate constant (k 1 ) is given by Eq.…”

“…Curci et al [26] proposed that in the oxidation of dibutyl sulfide with tert-butyl hydroperoxide (TBHP) catalyzed by VO(acac) 2 , the catalytically active species is a vanadium(V) and not a vanadium(IV) species. In the V(IV)-catalyzed reactions, the possible intermediate is a metal-oxo, metal-peroxo or bridging oxo complex of various types [25,27].…”