Isomerization of 14-hydroxy-17-ketosteroids: New examples of two-centered inversion of the C/D ring fusion and X-ray diffraction structural analysis of d,ℓ-3-methoxy-14β-hydroxy-8β, 9α-estra-1,3,5(10)-trien-17-one

d,-3-Methoxy-14-hydroxy-8,9-estra-1,3,5(10)-trien-17-one (I) undergoes two-centered isomerization in alkaline medium to d,-3-methoxy-14-hydroxy-8,9-estra-1, 3,5(10)-trien-17-one (II) in 70% yield. Under analogous conditions, natural isomer (II) is converted into synthetic isomer (I) in 20% yield. The crystalline and molecular structure of isomer (II) was established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2878–2883, December, 1991.     

Asymmetric synthesis of anti-β-hydroxy-α-amino acids

The stereoselective aldol addition reactions of chiral haloacetate enolates is reported. The conversion of these adducts to enantiomerically pure anti-β-hydroxy-α-amino acids is demonstrated (Eq 2).     

Stereoselective synthesis of α-hydroxy-β-amino acid derivatives from β-hydroxy-γ,δ-unsaturated sulfilimine

The first report on the use of N-sulfinyl benzylcarbamate for the preparation of N-Cbz sulfilimine from the corresponding sulfoxide is reported. The sulfilimine moiety is utilized as an intramolecular nucleophile for the regio- and stereoselective heterofunctionalization of an alkene to furnish a bromo carbamate which is used as a key advanced intermediate in the synthesis of representative α-hydroxy-β-amino acid derivatives.     

New β-amino-α-trifluoromethyl alcohols and their exploration in the synthesis of trifluoromethylated imidazole derivatives

Racemic and enantiomerically pure β-amino-α-trifluoromethyl alcohols were obtained via sequential nucleophilic trifluoromethylation of selected α-imino ketones, derived from arylglyoxals, and subsequent removal of the MeO or Ph(Me)CH substituent, respectively, located at the N-atom. The obtained products, containing a primary amino group, were used for the synthesis of imidazole N-oxides bearing a trifluoromethyl group as a part of the N(1)-alkyl chain. Imidazole N-oxides with an electron-withdrawing ester group at C(4) underwent spontaneous isomerization under the reaction conditions, and the corresponding imidazol-2-ones derivatives were isolated as final products.     

New ylidene derivatives of pyrrolo[2,1-α]isoquinoline-2,3-dione in the synthesis of dispiropyrrolidines

Russian Journal of Organic Chemistry -     

IBX in an ionic liquid: eco-friendly oxidation of 17α-methylandrostan-3β,17β-diol, an intermediate in the synthesis of anabolic oxandrolone

An easily available hypervalent iodine(V) reagent, 2-iodoxybenzoic acid (IBX) immobilized in the ionic liquid [bmim][Br] was found to be an efficient and eco-friendly protocol for the oxidation of 17α-methylandrostan-3β,17β-diol (1). At ambient temperature oxidation of 1 with IBX gave mestanolone (2) in good yield and with an increased stoichiometric amount of IBX, oxidation adjacent to the carbonyl functionality (α,β-unsaturation) occurred to give dehydrogenated 17β-hydroxy-17α-methyl-Δ¹-androsten-3-one (3) as the major product in a one-pot reaction. The product is easily obtained by extraction with diethyl ether and evaporation of the solvent.     

Laccase-mediated oxidation of the steroid hormone 17β-estradiol in organic solvents

Laccase-mediated oxidation of the steroid hormone 17β-estradiol 1 in organic solvents or in a biphasic system allowed the isolation of the C–C and C–O dimers 1a–d. Concerning the C–C dimers, the relative ratio of the symmetric 4-4′ 1c and asymmetric 4-2′ 1d products was influenced by the catalyst used. Both 1c and 1d were formed as an equimolar mixture of diastereomeric atropisomers.     

Stereocontrolled total synthesis of (±)-3β-hydroxy-9β-pimara-7,15-diene, a putative biosynthetic intermediate of momilactones

The total synthesis of (±)-3β-hydroxy-9β-pimara-7,15-diene (1), a putative biosynthetic intermediate of the momilactones, was accomplished stereoselectively. Our methodology for the synthesis of 1 featured the stereoselective construction of the C-13 quaternary carbon center via the aldol-Tishchenko reaction. 3β-Hydroxy-9β-pimara-7,15-diene (1) was identified by full-scan GC-MS analysis as an endogenous compound in elicited rice cells.     

Synthesis of (22E,24R)-ergosta-4,7-22-triene-3,6-dione and its 14α-hydroxy- and 9α,14α-dihydroxy derivatives

^4,7-3,6-Diketosteroids have been synthesized from ergosterol (1).Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus', 220141, Belarus', Minsk, Ul. Akad. Kuprevicha, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 354–358, May–June, 1999.     

α-Aminophosphonate derivatives of triethoxysilane for the synthesis of surface-modified silica

Abstract

A convenient synthetic route for the preparation of α-aminophosphonate derivatives of triethoxysilane, attractive precursors for silica surface functionalization, was developed. The condensation of commercially available APTES with carbonyl compounds followed by Pudovik reaction of imines with diethyl phosphite yielded desired N-phosphonomethyl functionalized (3-aminopropyl)triethoxysilanes in high yields without further purification. The chemical structures of obtained products were undoubtedly proved by ¹H, ¹³C and ³¹P NMR spectroscopy, elemental analysis and mass spectrometry.     

Enantioselective synthesis of anti-β-hydroxy-α-amido esters by asymmetric transfer hydrogenation in emulsions

Herein, we present two methods for an asymmetric transfer hydrogenation through the dynamic kinetic resolution of α-amido-β-ketoesters. These procedures yield the corresponding anti-β-hydroxy-α-amido esters in good yields and with good diastereo- and enantioselectivities. First, the scope of the reduction of α-amido-β-ketoesters by using triethylammonium formate azeotrope is examined. Then, an emulsion technology with sodium formate is explored, which allows for broader substrate scope, faster reaction times, and lower catalyst loading. Furthermore, these reactions are operationally simple and can be set up in air.     

Progress toward the total synthesis of 9β-hydroxyvertine: Construction of an advanced quinolizidine intermediate

Progress toward the total synthesis of 9β-hydroxyvertine 2 is described. Our approach involves a Petasis borono-Mannich reaction to assemble a key intermediate A, securing the correct configuration at H-9 and H-10 in the final targeted molecule. Subsequent formation of the quinolizidine framework B allowed the synthesis of an advanced intermediate containing all but the lactone moiety of 2. Our unsuccessful attempts at introducing this lactone feature are also described.     

Enantioselective synthesis of anti-β-hydroxy-α-amido esters via transfer hydrogenation

The asymmetric transfer hydrogenation of α-amido-β-keto esters to provide the corresponding anti-β-hydroxy-α-amido esters in good to excellent yields, diastereoselectivity, and enantioselectivity is reported. The procedure is operationally simple, and delicate handling of the catalyst is not necessary.     

New polymer-supported phosphonate reagents for the synthesis of Z-α,β-unsaturated esters

New polymer-supported phosphonate reagents have been prepared and evaluated for the synthesis of Z-α,β-unsaturated esters. High Z-selectivity was obtained using the reagent having two o-t-BuC₆H₄ groups.     

Measurement and correlation of densities and viscosities of 11α-hydroxy-16α,17α-epoxyprogesterone in chloroform

The densities and viscosities of 11α-hydroxy-16α,17α-epoxyprogesterone (HEPG) in chloroform were determined from 287.65 to 321.15 K. The viscosities were correlated using the Vogel-Tamman-Fulcher (VTF) equation, a good accuracy of the correlation being obtained.     

Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives

11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline 7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions.Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth.     

First total synthesis of 10α-hydroxy-4-muurolen-3-one and its C10-isomer

An efficient synthetic route to muurolane type sesquiterpenes starting from （R）-carvone, employing allylic diazene rearrangement and the ring closing methesis （RCM） reaction as key steps, is described. The first asymmetric total synthesis of （-）-10α- hydroxy-4-muurolen-3-one 11 and （-）-10β-hydroxy-4-muurolen-3-one C was accomplished. Through the total synthesis, the absolute configurations of the natural products A, B and C were established.     

First total synthesis of 10α-hydroxy-4-muurolen-3-one and its C10-isomer

An efficient synthetic route to muurolane type sesquiterpenes starting from (R)-carvone,employing allylic diazene rearrange-ment and the ring closing methesis (RCM) reaction as key steps,is described.The first asymmetric total synthesis of (-)-10α-hydroxy-4-muurolen-3-one B and (-)-10β-hydroxy-4-muurolen-3-one C was accomplished.Through the total synthesis,the absolute configurations of the natural products A,B and C were established.