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A new C-nor-D-homosteroid alkaloid, C27H43O6N, mp 171.5-173 degrees C, named pingbeimine C, was isolated from the bulb of Fritillaria ussuriensis Maxim. On the basis of IR, MS, 1HNMR and 13CNMR spectroscopic data, particularly X-ray crystallographic analysis, structure IV has been assigned to this alkaloid.
A new C-nor-D-homosteroidal alkaloid named Yibeinoside B was isolated from the bulb of Fritillaria pallidiflora Schrenk by column chromatographic techniques. The structure has been determined based on spectral and chemical data.
A main issue in modern synthetic organic chemistry, which deals with the preparation of natural products, pharmaceuticals, diagnostics, agrochemicals, and other important materials, is the improvement of efficiency, the avoidance of toxic reagents, the reduction of waste, and the responsible treatment of our resources. One of the ways to fulfill these goals is the development and use of domino processes, which consist of several bond-forming reactions and which allow the highly efficient synthesis of complex molecules starting from simple substrates. Herein, the combination of several catalytic bond-forming transformations is clearly most appropriate. The synthesis of the enantiopure alkaloid (-)-hirsutine 22, which has a strong inhibitorial effect on influenza A viruses, was accomplished using a biomimetic domino Knoevenagel-hetero-Diels Alder-solvolysis-hydrogenation process. In a similar way the alkaloids (+)-dihydrocorynantheine 23 and (-)-dihydroantirhine 24 as well as heterosteroids 62, D-homosteroids 65 and 68, and azasteroids 25 are prepared. In addition, novel steroid alkaloids 26 are accessible by a combination of the formation of an iminium salt, a hydride shift, and an alkylation. The anti-leukemic pentacyclic (-)-cephalotaxine 27 is obtained by a combination of two Pd-catalyzed reactions.
By use of the aza Diels-Alder reaction a series of aminoisoquinolines and aminoquinolines have been elaborated to provide an effective synthesis of diverse diazasteroids. In particular, representative 1,11-diaza-, 3,11-diaza-, and 4,11-diazasteroids have been synthesized from cyclopentadiene. From dihydropyran a 4,11-diaza-15-oxa-D-homosteroid has been obtained.
Synthetic corticosteroids are widely used as anti-inflammatory agents. Mechanisms of their degradation continue to be studied. D-ring homoannulation is a well-known metabolic pathway for steroids in vivo. The rearrangement with aluminium trichloride of the commercial anti-inflammatory drugs hydrocortisone, cortisone and dexamethasone is here presented. The structures of the corresponding 17a-keto-17-hydroxy-D-homosteroids are established by mono- and two-dimensional NMR analysis. Inversion of the alpha-configuration of C-16 is observed in the Lewis acid assisted D-homoannulation of dexamethasone.
Preparative-scale fermentation of the known C-nor-D-homosteroidal jerveratrum alkaloid jervine with Cunninghamella elegans (ATCC 9245) has resulted in the isolation of (-)-jervinone as the major metabolite. In addition, C. elegans ATCC 9245 was able to epimerize C-3 of jervine, producing 3-epi-jervine. This epimerization reaction was similar to that reported for tomatidine, the known spirosolane-type Solanum alkaloid. The structure elucidation of both metabolites was based primarily on 1D- and 2D-NMR analyses.
Preparative-scale fermentation of the known C-nor-D-homosteroidal alkaloid veratramine (1) with Nocardia species ATCC 21145 has resulted in the isolation of three new metabolites, 2-4. The structure elucidation of these compounds was conducted primarily by 2D NMR analysis. The microbe Nocardia species ATCC 21145 was able to metabolize rings A and B of veratramine but failed to metabolize its nitrogen-containing side chain, an observation consistent with previous fermentation studies on steroidal alkaloids.
New compounds derived from the 3-methyl and 3-benzyl ethers of a D-secoestrone aldehyde were synthesized. In the presence of different Lewis acids D-homosteroids could form. These reactions which can be explained by an intramolecular Prinstype mechanism follow high stereoselectivity and reactivity and lead to compounds containing 16 beta-oriented halogens in the sterane skeleton. The formation and reaction of the imines derived from the aldehyde and aniline as well as substituted anilines provide a highly efficient access to steroid derivatives. The steroid alkaloids are of pharmacological interest.
A new C-nor-D-homosteroidal alkaloid was isolated from the bulbs of Fritillaria thunbergii Miq. with peimine (I) and peiminine (II), named zhebeinine (III), C27H45O3N, mp. 240-242 degrees C. On the basis of the IR, 1HNMR, 13CNMR and MS of zhebeinine (III), the structure of zhebeinine (III) has been established as 5 alpha, 14 alpha-cevanine-3 beta, 6 alpha, 20 beta-triol.
The mammalian group IIA secretory phospholipase A(2) (sPLA(2)) is believed to play an important role in inflammation and cell injury. The present study underlines the importance of group IIA sPLA(2) in the regulation of iNOS. Treatment of cells with sPLA(2) induced protein expression and mRNA accumulation of iNOS in a dose-dependent manner. The pretreatment of cells with rho-BPB or SCA, selective sPLA(2) inhibitors, inhibited sPLA(2)-induced iNOS expression. sPLA(2) stimulated the simultaneous activation of two classes of mitogen-activated protein kinases ERK and JNK, but did not stimulate p38 MAPK. PD98059, a selective MEK inhibitor, inhibited sPLA(2)-induced nitrite production and iNOS expression as well as ERK phosphorylation. In addition, pretreatment of rho-BPB or SCA also resulted in inhibition of sPLA(2)-induced ERK phosphorylation. The sPLA(2) signaling mechanisms involving the activation of transcription factor NF-kappaB were studied in the same cells. That stimulation of cells with sPLA(2) caused NF-kappaB activation in a time-dependent manner was shown by the detection of NF-kappaB-specific DNA-protein binding and by IkappaBalpha degradation. sPLA(2)-induced NF-kappaB activation was prevented in the presence of rho-BPB. Furthermore, the NF-kappaB inhibitor PDTC suppressed sPLA(2)-induced nitrite production and iNOS expression as well as IkappaBalpha degradation. The results strongly suggest that group IIA sPLA(2) induces iNOS in macrophages and that this induction occurs through ERK and NF-kappaB.
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A biomimetic approach was employed to shed light on the nature of chemical reactions occurring in the covalent inactivation of phospholipase A(2) (PLA(2)) by scalaradial (1), a marine dialdehyde terpenoid endowed with potent anti-inflammatory activity. To this end, a detailed study of the reaction profile between the nitrogenous nucleophile isopropylamine and scalaradial was performed under biologically relevant conditions.