Mass spectra of 1,19-epoxycardenolides
The mass spectra of six 18,19-epoxycardenolides (ECs) with various substituents in the 3β position — OH, OAc, rhamnosyloxy have been studied. In all the spectra the contribution of the fragments characteristic for cardenolides formed by the cleavage of the bonds of rings C and D were lowered. The strongest peaks were those of ions with m/z 259, 272, and 285 arising on the splitting out of the elements of rings A and B. It was established by the metastable defocusing (MD) method that in the case of the 3β-ols these fragments are formed from M+ and in the case of acetyl derivatives, in addition, they may arise from the (M — AcOH)+ ions. The spectra of the epoxycardenolides were compared with the structure of 3β,5β,14β,19-tetrahydroxycardenolide (strophanthidol) and its 3β-monoacetate and 3β,19-diacetate. The MD spectra and elementary compositions of the ions showed that other mass-spectrometric conditions strophanthidol monoacetate decomposes partially in the form of the 8,19-epoxycardenolide.
A biocatalytic hydroxylation-enabled unified approach to C19-hydroxylated steroids
Steroidal C19-hydroxylation is pivotal to the synthesis of naturally occurring bioactive C19-OH steroids and 19-norsteroidal pharmaceuticals. However, realizing this transformation is proved to be challenging through either chemical or biological synthesis. Herein, we report a highly efficient method to synthesize 19-OH-cortexolone in 80% efficiency at the multi-gram scale. The obtained C19-OH-cortexolone can be readily transformed to various synthetically useful intermediates including the industrially valuable 19-OH-androstenedione, which can serve as a basis for synthesis of C19-functionalized steroids as well as 19-nor steroidal drugs. Using this biocatalytic C19-hydroxylation method, the unified synthesis of six C19-hydroxylated pregnanes is achieved in just 4 to 9 steps. In addition, the structure of sclerosteroid B is revised on the basis of our synthesis. C19 hydroxylation is a unique feature of some bioactive steroids. Here, the authors developed a direct C19 hydroxylation approach to scalably access 19-OH-cortexolone in the host T. cucumeris and then converted the product into various pharmaceutically useful products via chemical synthesis.
Interaction of Diclofop-Methyl and MCPA on Wild Oats (Avena fatua)
Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatua L.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.