Completely stereocontrolled aldol reaction of chiral β-amino acids.

A general protocol to independently access stereoisomerically pure β'-hydroxy-β-amino acid derivatives that is based on dibutylboron triflate-mediated aldol reaction of suitably protected β-amino acids bearing chiral oxazolidinone auxiliary is reported. The method smoothly afforded syn-aldol (α,β'-syn) products in pure form and excellent isolated yield. Both α,β-syn and α,β-anti isomers are readily accessible solely through the choice of the oxazolidinone chirality.

Total synthesis of manzamine A and related alkaloids.

Total syntheses of three structurally complex marine natural products, manzamine A, ircinol A, and ircinal A, are reported. The route pivoted on the construction of a late-stage protecting-group-free pentacyclic enol triflate coupling partner, from which all three family members were accessed divergently via palladium-catalyzed reactions. The rapid synthesis of this key pentacyclic enol triflate was achieved by a highly convergent union of five fragments through a stereoselective Michael addition, a three-component nitro-Mannich lactamization cascade, an unprecedented and highly stereoselective reductive nitro-Mannich cyclization cascade, a stereoselective organometallic addition, and a Z-selective alkene ring-closing metathesis.

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.

Synthesis and analytics of 2,2,3,4,4-d5-19-nor-5alpha-androsterone--an internal standard in doping analysis.

A short and efficient synthesis of pentadeuterated 2,2,3,4,4-d5-19-nor-5alpha-androsterone 7 starting from 19-norandrost-4-ene-3,17-dione 1 by a d1-L-Selectride mediated stereo- and regioselective reduction of the 3-keto group is presented. The use of compound 7 as internal standard for the detection of anabolic steroids via mass spectrometric techniques such as gas chromatography-mass spectrometry (GC-MS) is discussed.

Crotylation versus propargylation: two routes for the synthesis of the C13-C18 fragment of the antibiotic branimycin.

The C13-C18 fragment 3 of the novel antibiotic branimycin was prepared along two highly stereocontrolled routes. The first one uses a standard Roush crotylation protocol, whereas the second one proceeds via an allenyl silane propargylation with unexpected stereochemical consequences, which are discussed in detail.

A tether controlled exo-selective trans-annular Diels-Alder (TADA) reaction.

[reaction: see text] A fully substrate controlled stereoselective route to construct cis-hexahydronaphthalene 4 is described starting from nonracemic butenolide 6. The key step is an exo-selective transannular Diels-Alder reaction (TADA) of tetraene 5, whose intrinsic constraint allows selective formation of one stereodefined product. Compound 4 is a key intermediate in the synthesis of the novel antibiotic branimycin (1).

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.

First synthesis of a pentadeuterated 3'-hydroxystanozolol--an internal standard in doping analysis.

The first synthesis of 16,16,20,20,20-pentadeuterio-3'-hydroxystanozolol (8) in 26% yield over nine steps is described using moderately priced starting materials and economic amounts of reagents. Compound 8 can be used as an internal standard in screening procedures for anabolic steroids as well as for the quantification of stanozolol metabolites via mass spectrometric techniques, such as LC-MS or gas chromatography-mass spectrometry (GC-MS).

A facile and high yielding synthesis of 2,2,3,4,4-d5-androsterone-beta-D-glucuronide--an internal standard in dope.

A facile six-step synthesis of 2,2,3,4,4-d5-androsterone-beta-D-glucuronide (1) starting from epiandrosterone (2) in 63% yield is described and compared with several alternative synthetic pathways. Compound 1 can be used as an internal standard in screening procedures for anabolic steroids to monitor the hydrolysis step of the steroid glucuronides prior to gas chromatography-mass spectrometry (GC-MS) analysis. Thus, a time consuming solid-phase extraction step to remove possible hydrolysis inhibitors can be omitted.