Construction of the Bicyclic Carbon Framework of Euphosalicin.

Our studies toward the total synthesis of the natural product euphosalicin (1) are presented. Different approaches targeting key intermediates are described, the synthesis of which includes findings on asymmetric dihydroxylations and ring-closing enyne metatheses (RCEYM). Their connection allowed the isolation of highly advanced precursors for studies on macrocyclizations. Our efforts culminated in the preparation of the unique C11/C12 (Z) isomer of the C13 nor methyl skeleton of euphosalicin (1).

Efforts toward the Total Synthesis of Elisabethin A.

We describe our efforts toward the total synthesis of the natural product elisabethin A. The first route was guided by the proposed biosynthesis, assembling the 6,6-ring system before forming the five-membered ring including the quaternary carbon. The second approach includes a high yielding cyclization under Mitsunobu conditions as a key step. It allowed the preparation of an unusual and highly functionalized bicyclic 6,5-spiro compound. Both routes share a common advanced precursor obtained from an "underdeveloped" Claisen rearrangement of an aryl dienyl ether.

Synthesis of human long-term metabolites of dehydrochloromethyltestosterone and oxymesterone.

We herein report the synthesis of the long-term metabolites "M4" (IUPAC: 4-chloro-17-hydroxymethyl-17-methyl-18-norandrosta-4,13-dien-3-ol) of dehydrochloromethyl-testosterone (DHCMT, Oral Turinabol) and "Oxy M9" (4-hydroxy-17ß-hydroxymethyl-17α-methyl-18-norandrosta-4,13-dien-3-one) of oxymesterone (Oranabol). Both compounds were derived from a common synthetic route starting from dehydroepiandrosterone acetate. Four different stereoisomers were evaluated for metabolite M4. The previously assigned structure could be corrected regarding the C-3 and C-17 stereocenters.

Synthesis of a human long-term oxymetholone metabolite.

A long-term metabolite of the doping agent oxymetholone (OXM-M2, 17ß-hydroxymethyl-2,17α-methyl-18-norandrost-13-en-3-one) which has been identified by GC-MS/MS was synthesized from commercially available materials. Two efficient synthetic routes to access both C-17 epimers of tentative metabolites were developed. The identity and molecular configuration of the in vivo metabolite: 17ß-hydroxymethyl-2α,17α-methyl-18-norandrost-13-en-3-one was confirmed by single crystal X-ray diffraction.

Synthesis and structural elucidation of a dehydrochloromethyltestosterone metabolite.

The human urinary long-term metabolite "M3" (4-chloro-17ß-hydroxymethyl-17α-methyl-18-norandrost-13-en-3-ol) of the common doping agent DHCMT has thus far been detected via GC/MS-MS, creating ambiguities concerning its absolute configuration. Its structure was elucidated via the synthesis of all eight possible stereoisomers with 17ß-hydroxymethyl configuration. The highlights of the synthesis consist of a novel first generation approach to 4ß-chloro-5ß compounds as well as a divergent route which allows easy access to the remaining A-ring chlorohydrins.

Synthesis of 17ß-hydroxymethyl-17α-methyl-18-norandrosta-1,4,13-trien-3-one: A long-term metandienone metabolite.

The goal of this work was a good-yielding chemical synthesis of a metandienone metabolite which is of interest in doping analysis. 20ßOH-NorMD (IUPAC: 17ß-hydroxymethyl-17α-methyl-18-norandrosta-1,4,13-triene-3-one) has been identified as a long-term urinary metabolite which can be detected and attributed to metandienone up to almost 3weeks after exposure. The chemical synthesis of its epimer 20αOH-NorMD has been described before, as was an enzymatic synthesis of 20ßOH-NorMD, but no chemical synthesis was published.

Total synthesis of branimycin: an evolutionary approach.

The first total synthesis of the macrolactone antibiotic branimycin (4) has been described. The key disconnection leads to a cis-dehydrodecalone core and a polyketide side chain which are connected via organometallic addition. The dehydrodecalone core was targeted via altogether five different approaches featuring various kinds of chiral elements and ring-closing methodology. In the end the most successful method starting from diepoxynaphthalene 109 was chosen to carry on with the synthesis. Thus the oxygen functions and carbon appendages were introduced via organometallic desymmetrization reactions to generate epoxy ketone 107, to which vinyl iodide 11 was added after conversion into the organolithium species. The synthesis was completed by introducing the ester side chain via Michael addition and subsequent macrolactonization.

A non-Diels-Alder approach to the cis-decalin core of branimycin.

The synthesis of the highly substituted cis-decalin core of branimycin has been accomplished. A catalytic copper mediated SN2' opening of oxabicycle 7 with Grignard reagent and ring-closing metathesis served as key transformations.

cis-decalins from quinic acid: toward a synthesis of branimycin.

[reaction: see text] Starting from (-)-quinic acid an efficient synthesis of highly functionalized cis-alpha,beta-unsaturated ketone 3, an advanced precursor of branimycin, has been accomplished via two key step reactions: a ring closing metathesis reaction to prepare the cis-decalin system, and a highly stereoselective epoxidation reaction.

Toward the synthesis of the antibiotic branimycin: novel approaches to highly substituted cis-decalin systems.

A variety of highly functionalized cis-decalin systems have been prepared by means of the stereoselective transannular Diels-Alder (TADA) reaction of a (Z,E,Z,Z)-tetraene macrolide, and by means of intramolecular nitrile oxide olefin (INOC) or ring-closing metathesis (RCM) annulations to quinic acid derivatives.

Total synthesis of the microtubule stabilizing antitumor agent laulimalide and some nonnatural analogues: the power of Sharpless' asymmetric epoxidation.

Three different routes are described for the synthesis of deoxylaulimalide (3), which is the immediate precursor of the marine sponge metabolite laulimalide (1). These routes mainly differ with respect to their ring closing step. Thus, route 1 uses a Still-Gennari olefination, route 2 a Yamaguchi lactonization, and route 3 an intramolecular allylsilane-aldehyde addition for establishing the macrocyclic structure. The unprotected deoxy derivative 3 was subjected to Sharpless' asymmetric epoxidation (SAE). With (R,R)-tartrate the 16,17-epoxide laulimalide (1) is formed selectively, whereas (S,S)-tartrate generates the 21,22-epoxide 142. This demonstrates the high reagent control involved in the SAE process, which in this case is used to achieve high stereo- and regioselectivity. Laulimalide and some derivatives thereof have been tested with respect to antitumor activity and compared to standard compounds paclitaxel and epothilone B.