Autooxidation of Δ17(20)-20-hydroxy derivatives of steroids. Synthesis of 3β-acetoxy-17α-hydroperoxy-16α-methylpregn-5-en-20-one and its reduction to 17α-hydroxy derivative

An efficient procedure was proposed for the synthesis of 3β-acetoxy-17α-hydroperoxy-16α-methylpregn-5-en-20-one. Optimal conditions were found for the combined process including 1,4-addition of methylmagnesium bromide at the Δ¹⁶-20-oxo fragment of dehydropregnenolone acetate and autooxidation of resulting bromomagnesium 3β-acetoxy-16α-methylpregna-5,17(20)-dien-20-olate. The subsequent reduction of the 17α-hydroperoxy group and hydrolysis of the 3β-acetoxy group afforded 17α-hydroxy-16α-methyl-substituted dehydropregnenolone acetate and its 3-hydroxy analog in high yield.     

Transformed steroids—65 : Mechanism of the rearrangement of steroid oxiranes by treatment with Grignard reagents

Rearrangement of steroid acetoxy-epoxides under the action of MeMgX was studied with the use of deuterated analogs, epimeric at C-20 (20-deutero-20-acetoxy-16α,17α-epoxysteroids). 3β,16α,20-Trihydroxy-20-methylpregnenes resulting in this case contained all the deuterium. Thus this rearrangement is proved to involve a hydride shift. Interaction of a 16α-acetoxy-17α,20α-epoxysteroid with MeMgX does not lead to above compounds. This fact suggests the mechanism of this novel rearrangement as proceeding via the formation of chelate complex with the participation of the carbonyl oxygen atom of the acetoxy-group and oxygen atom of the oxide ring followed by intramolecular 20 → 17 hydride shift. Some stereochemical aspects of this reaction are discussed.     

Germylated steroids

16α-Trichlorogermyl-3β-acetoxypregnan-20-ones react with MeMgBr to form the corresponding stable 16α-trimethylgermyl derivatives, which were further converted to 16α-trimethylgermylprogesterones. Analogous 16α-trichlorogermyl isomers do not react with the Grignard reagents.     

Bismuth(III) triflate-catalyzed rearrangement of 16α,17α-epoxy-20-oxosteroids. Synthesis and structural elucidation of new 16α-substituted 17α-alkyl-17β-methyl-Δ-18-norsteroids

The use of bismuth(III) triflate for the rearrangement of 16α,17α-epoxy-20-oxosteroids is reported. The reactions occur under truly catalytic conditions to afford novel 17α-alkyl-17β-methyl-Δ¹³-18-nor products bearing different O-containing substituents at C16. When the reaction is performed in the absence of acylation agent a mixture of isomeric 16α- and 16β-hydroxy derivatives is obtained, whereas when carried out in the presence of such reagents, the reaction selectively affords the corresponding 16α-acyl rearranged products. The chemoselective rearrangement of 5β,6β;16α,17α-diepoxy-20-oxopregnan-3β-yl acetate to afford a ‘backbone’ rearranged product bearing the 16α,17α-epoxide group is also reported. Some mechanistic considerations are provided. All rearranged products were the subject of comprehensive structural elucidation, by the use of X-ray crystallography and 2D NMR.     

Transformed steroids. 193. Synthesis of 16α,17α-isopropylidene derivatives of pregn-4-ene-9α,16α,17α,21-tetraol-3,20-dione and its 17α-thioanalog

A study was carried out on the pathways for the transformation of 16α,17α-epoxypregn-4-ene-9α,21-diol-3,20-dione to give 16α,17α-isopropylidene derivatives of pregn-4-ene-9α,16α,17α,21-tetraol-3,20-dione and its 17α-thioanalog. The key step in this pathway is thecis-cleavage of the 20-carboethoxyhydrazone of this epoxide by acetic and thioacetic acids and subsequent condensation of the products formed with acetone. This pathway is an efficient approach to the synthesis of the 16α,17α-dioxolane derivative and is equally efficient for preparation of the thioanalog, namely, 16α,17α-isopropylidenepregn-4-ene-9α,16α,21-triol-17α-thiol-3,20-dione, which has already been synthesized by an alternative method.     

Alkaloids ofNitraria schoberi. Structure of dihydronitraraine

The structure of dihydronitraraine (I) has been established on the basis of the results of a study of its chemical properties and spectral characteristics and also of a correlation with nitraraine. An internal quaternary salt of (I) has been obtained and, by means of a directed change in the configuration at C₃ in (I), the complete stereochemistry of the nitraraine and dihydronitraraine molecules have been determined: (±)-16-hydroxymethyl-3α,15α,20α-yohimb-16-ene and (±)-16β-hydroxymethyl-3α,15α,20α-yohimbane, respectively.     

A further study of the substrate specificity in the reduction of 20-oxosteroids with a culture ofActinomyces roseochromogenus

Chemistry of Natural Compounds - A culture ofActinomyces roseochromogenus ATCC 3347 reduces 17-hydroxy- and 16α, 17α-epoxy-20-oxopregnenes to the corresponding 20α-alcohols, but is...     

Triterpene glycosides ofAstragalus and their genins XLV. The chemical transformation of cycloartanes 1. Synthesis of 25-norglycosides

Literature information is given on the current state of the study of the chemical transformation of cycloartane triterpenoids. A method has been developed for the transformation of the genin part of glycosides of 20,24-epoxycycloartan-25-ols with retention of the carbohydrate constituents. Three 25-norglycosides have been synthesized from natural cyclosieversigenin glycosides, namely 16β-acetoxy-3β,6α-dihydroxy-20R,25-norcycloartan-20,24-olide 3-O-[O-α-L-arabinopyranosyl-(1→2)-β-D-xylopyranoside] 6-O-β-D-xylopyranoside (VIII), sodium 3β,6α,16β,20-tetrahydroxy-20R,25-norcycloartan-24-oate 6-O-β-D-glucopyranoside 3-O-β-D-xylopyranoside (XII), and 20R,25-norcycloartane-3β,6α,16β,20,24-pentaol 6-O-β-D-glucopyranoside 3-O-β-D-xylopyranoside (XIII).     

Two new diterpenoids from Isodon serra

From the aerial part of Isodon serra,two new ent-6,7-seco-kaurane-type diterpenoids,15α,20β-dihydroxy-6β-methoxy-6,7- seco-6,20-epoxy-1,7-olide-ent-kaur-16-ene (1) and 6α,15α-dilaydroxy-20-aldehyde-6,7-seco-6,11α-epoxy-1,7-olide-ent-kaur-16- ene (2) were isolated.Their structures were elucidated by spectroscopic means.     

New ent-kaurane-type diterpenoids from Isodon nervosus

Two new ent-kaurane-type diterpenoids,6β,7β,13α-trihydroxy-1α-acetoxy-7α,20-epoxy-ent-kaur-16-en-15-one（1）and 15β- hydroxy-6,7-seco-6,11β：6,20-diepoxy-1α,7-olide-ent-kaur-16-ene（2）were isolated from the Isodon nervosus,and the structures were elucidated by spectroscopic analysis.     

Reaction of 5β,6β-epoxy-16α,17α-cyclohexapregnane with methylmagnesium iodide

On treatment with methylmagnesium iodide, 3β-acetoxy-5β,6β-epoxy-16α,17α-cyclo-hexapregnan-20-one undergoes 3-O-deacetylation along with the opening of the 5β,6β-epoxide ring to form 5α-methyl-6β-hydroxy steroid and the 6α-methyl-6β-hydroxy isomer, the 20-keto group remaining intact.     

Transformed steroids. 123. Synthesis of 5α(H)- and 5α(OH)-6-ketosteroids with an additional 17α,20ξ-dihydroxytetrahydropyran ring E

The paper is devoted to the synthesis of 3,17α,20-trihydroxy-16β,23-epoxy-21,24-dinor-5αH-cholan-6-one and 3,5α,17α,20-tetrahydroxy-16β,23-epoxy-21,24-dinorcholan-6-one and derivatives of them. It has been shown that the reduction of 3,17α-dihydroxy-16β,23-epoxy-21,24-dinorchol-5-en-20-one with sodium tetrahydroborate and with diborane takes place stereospecifically with different spatial directivities: in the products of diborane reduction, ring E exists in the boat form, as has been shown by¹H and¹³C NMR methods. The trans linkage of rings A/B in the modified steroids has been confirmed by their circular dichroism spectra.     

Oxydation photochimique d'amines tertiaires et c'alcaloïdes XI: Photooxydation sensibilisée de la corynanthéidine. Transformation de dérivés de type corynanthéine en dérivés de type sarpagine

1 - Benzenesulfonyl - 17 - methoxy - 5α - cyano - 16ζ, 17 - 2α, 7α - tetrahydrocorynantheidine 21c, which was obtained by photosensitized oxidation of 1 - benzenesulfonyl - 17 - methoxy - 16ζ, 17 - 2α, 7α - tetrahydro-corynantheidine 20d effected in the presence of KCN, has been transformed into 1- benzene - sulfonyl - 2α, 7α - 20α, 19 - tetrahydro - 10 - deoxysarpagine 24b. A mechanism is proposed for the formation of 6α - hydroxy - 5α - cyano - 2α, 7α - dihydrocroynantheidine when 1-trifluoroacetyl - 2α, 7α - dihydro - corynantheidine was irradiated in the presence of rose bengale, oxygen and KCN.     

Two new diterpenoids from Isodon eriocalyx

Isodoneriocalyx(Dunn)Hara(Labiatae).Ithasbeenusedasfolkmedicinetotreatsorethroat,inflammationaswellasreducingbloodpressure'.Previousstudiesonthisgenushaverevealed,anumberofditerpenoidspossessvariousbioactivitiessuchasanti-tUmorandanti-bacterial='3act...     

Practical synthesis of 16α-bromo-17α-hydroxysteroids via a Raney Ni-catalyzed bromide exchange reaction

D-ring modified glucocorticoids are attractive synthetic targets owing to their broad application in medicinal chemistry. Herein, we reported a practical synthesis of 16α-bromo-17α-hydroxysteroids from easily available 16β-bromo isomers via a Raney Ni-catalyzed bromide exchange reaction. The catalytic Finkelstein-type reaction features high yield, mild reaction condition, short reaction time and simple operation. The method provided an efficient approach to prepare 17α-hydroxy-15-pregnen-20-ones.     

A new synthesis of potent antitumor saponin OSW-1 via Wittig rearrangement

OSW-1 and its analogues in which thiophene ring was introduced at the side chain were synthesized employing Wittig rearrangement of 17E(20)-ethylidene-16α-(4′-methyl-2′-thienyl)methyloxy steroid. The synthesis required nine steps from the known 17E(20)-ethylidene-16α-hydroxy steroid in 15.6% overall yield.     

Photooxygenation of Pregnanes

The course of the singlet‐oxygen reaction with pregn‐17(20)‐enes and pregn‐5,17(20)‐dienes was studied to compare the reactivity of the two alkene moieties present in some steroid families. Thus, from commercially available (3β,5α)‐hydroxy‐androstan‐17‐one and (3β)‐3‐hydroxyandrost‐5‐en‐17‐one, the following 3‐{[(tert‐butyl)dimethylsilyl]oxy}‐substituted, 17(20)‐unsaturated pregnanes were prepared (see Fig. 1): (3β,5α)‐21‐norpregn‐17(20)‐ene 1 ; (3β,5α,17Z)‐pregn‐17(20)‐ene 2 , (3β,5α,16α,17E)‐pregn‐17(20)‐en‐16‐ol 3 , (16β,5α,17E)‐pregn‐17(20)‐en‐16‐ol 4 , (3β,5α,16β,17E)‐pregn‐17(20)‐en‐16‐ol acetate 5 , (3β,16α)‐21‐norpregna‐5,17(20)‐dien‐16‐ol 6 , (3β,16α,17E)‐pregna‐5,17(20)‐dien‐16‐ol 7 , (3β,17Z)‐pregna‐5,17(20)‐diene 8 , (3β,17E)‐pregna‐5,17(20)‐dien‐21‐ol 9 and (3β,17E)‐5,17(20)‐dien‐21‐ol acetate 10 . The oxygenated products (see Fig. 2) obtained from 1 – 10 and ¹O₂, generated by irradiation of Rose Bengal in ³O₂‐saturated pyridine solution, were characterized by ¹H‐, ¹³C‐NMR, and MS (EI, FAB, HR‐EI, ESI‐ and UV‐MALDI‐TOF) data. Major products were those formed by the ene reaction involving as intermediates the corresponding hydroperoxides and the cyclic tautomers of the allylic hydroperoxides, i.e., the corresponding oxiranium oxide‐like intermediate (Scheme 5).     

Steroidal quinoxalines

The treatment of 3β-hydroxy-16α-bromo-5α-androstan-17-one, 3β-acetoxy-16α-bromo-5-androsten-17-one and 21-bromo-5-pregnen-3β-ol-20-one with 4,5-dimethyl-o-phenylenediamine gave substituted quinoxalines. Hydrolysis of 3β-acetoxy-5-androsteno[16,17-b]-6′,7′-dimethylquinoxaline produced the corresponding 3β-hydroxy compound. 3-Oxo-4-androsteno[16,17-b]-6′,7′-dimethylquinoxaline was obtained by Oppenauer oxidation of the corresponding alcohol.     

Chemistry of ayurvedic crude drugs—V : Guggulu (resin from commiphora mukul)—5 some new steroidal components and,stereochemistry of guggulsterol-I at C-20 and C-22

20α-hydroxy-4-pregnen-3-one (5), 20β-hydroxy-4-pregnen-3-one (6), 16β-hydroxy-4,17(20)Z-pregnadien-3-one (4) and 16α-hydroxy-4-prenen-3-one (10) have been isolated as new steroidal components of the gum-resin from Commiphora mukul. A simple procedure for the synthesis of 4 is described. Chirality at C-20, C-22 in guggulsterol-I (3) has been clarified.     

Vinmajorines C – E,Monoterpenoid Indole Alkaloids from Vinca major

Three new monoterpenoid indole alkaloids, vinmajorines C–E ( 1 – 3 ), along with 18 known analogues ( 4 – 21 ), were isolated from the whole plants of Vinca major. The new structures were elucidated as (5α,15β,16R,17α,19β,20α,21β)‐10,17‐dimethoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐19‐ol ( 1 ), (5α,15β,16R,17α,20α,21β)‐10‐methoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐17‐ol ( 2 ), and (5α,15β,16R,17α,20α,21β)‐10‐methoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐17‐yl acetate ( 3 ), respectively, by extensive NMR and MS analysis and comparison with known compounds. Compounds 1 – 3 were evaluated for their cytotoxic activities against five human cancer cell lines, compounds 1 and 3 showing moderate cytotoxic activities.