Few constraints limit the design of quinone methide-oligonucleotide self-adducts for directing DNA alkylation.

Nucleotide sequences minimally containing adenosine, cytosine or guanosine are sufficient to form intrastrand oligonucleotide quinone methide self-adducts reversibly for subsequent alkylation of complementary DNA. The general lack of sequence restrictions should now allow for alkylation of most any target of interest although reaction is most efficient when the self-adducts contain guanine residues and do not form hairpin structures.

A general and stereoselective route to alpha- or beta-galactosphingolipids via a common four-carbon building block.

A general synthetic strategy toward alpha- or beta-galactosylceramides and their analogues from 3-azido-2-O-benzyl-1-O-(4-methoxybenzyl)butane-1,2,4-triol is described. The key steps for the installation of the main lipid chain are either a diasteroselective alkynylation reaction yielding the 4R stereocenter of phytosphingosine or a Wittig olefination generating the trans double bond of sphingosine. The methodology allows the preparation of different glycolipids with variations in the structure of the sphingoid base. In particular, three alpha-GalCer-related compounds have been synthesized and evaluated for their ability to activate CD1d-restricted T-cells.

Stereoselective synthesis and immunogenic activity of the C-analogue of sulfatide.

[Structure: see text] The C-sulfatide 1b was synthesized through a [2,3]-Wittig sigmatropic rearrangement and a Horner-Wadsworth-Emmons olefination as the key steps. The C-analogue 1b is less immunogenic than natural sulfatide 1a, but induces a preferential secretion of the proinflammatory cytokine IFN-gamma.

Structure elucidation of new compounds from acidic treatment of the progestins gestodene and drospirenone.

Gestodene acidic treatment afforded a single rearrangement product, namely 13-beta-ethyl-18,19-dinorpregna-4,14,16-trien-3,20-dione 3, which was originated through HCl-catalyzed Rupe rearrangement. Drospirenone acidic treatment yielded two epimeric lactones by addition of HCl to the 6beta,7beta-cyclopropane ring, namely 7beta-(chloromethyl)-15beta,16beta-methylene-3-oxo-17beta-pregn-4-ene-21,17-carbolactone 4 and 7beta-(chloromethyl)-15beta,16beta-methylene-3-oxo-17alpha-pregn-4-ene-21,17-carbolactone 5. The structure of the compounds was assessed by spectroscopic and crystallographic methods.

Crystal structures of 10alpha-gon-5-enes from the synthetic pathway to desogestrel.

X-ray crystallographic studies performed on the product of the ketalization reaction of 13beta-ethyl-11alpha-hydroxy-gon-5-ene-3,17-dione have lead to the unequivocal assignment of the 10alpha stereochemistry to C10, showing that an inversion of configuration occurred during formation of the 3,17-diketal. From the Swern oxidation of this compound, 11alpha-(methylthio)methoxy-10alpha-gonene was obtained as the major product instead of the desired 11-ketone. Modeling studies showed that the configurational instability at C10 is determined by the presence of the 11alpha-hydroxyl group.

Crystal structure of steroidal monoenes obtained by reduction of the aromatic A ring of 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11alpha,17beta-diol.

The crystal structures of 13-ethyl-gona-1(10)-ene-11alpha,17beta-diacetate (3b) and 13-ethyl-10alpha-gona-4-ene-11alpha,17beta-diacetate (5b), two steroidal monoenes obtained as minor products from the reduction, then acetylation, of the aromatic A ring of 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11alpha,17beta-diol (1), were determined by X-ray diffraction. The conformations of the rings A, B, C, and D and the unusual stereochemistry at C-10 of the 10alpha-gona-4-ene (5b) are discussed.

Base promoted air oxidation of 13beta-ethyl-11-methylenegon-4-en-17-one.

The structure of 13-ethyl-11-methylene-18,19-dinor-17alpha-pregn-4-en-20-yn-16beta,17-diol (3, 16beta-OH desogestrel), a by-product obtained in the last step of the synthesis of desogestrel (1) by reaction of monolithium acetylide-ethylenediamine complex with 13beta-ethyl-11-methylenegon-4-en-17-one (2), is here reported. The structural assignments were supported by NMR 1H-, 13C-, 1H-1H COSY, 1H-13C HSQC, COLOC) and mass spectroscopy, and the configuration at the C-16 and C-17 stereocentres was established by X-ray crystallography. When the same 17-ketoderivative 2 was treated with a non-alkylating base, such as potassium tert-butoxide, instead of the expected 16-hydroxylated ketone, a dimeric product, 13beta-ethyl-16-[2'-(des-D-13"-carboxy-13"beta-ethyl-11"-methylenegon-4"-en-14"-yl)-ethyliden]-11-methylenegon-4-en-17-one (4), was isolated in good yield; it was characterized by NMR, mass, ultraviolet spectroscopy, and chemical transformations. Compounds 3 and 4 originate from the high reactivity of the 16-methylenic position of the 17-keto substrate (2) toward molecular oxygen under basic conditions.

Reduction of aromatic steroidal A rings by lithium in ethyl amine.

The reduction of 3-methoxy-estra-1,3,5(10)-trien-17beta-ol (6) and 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11alpha,17beta-diol (2) by lithium in ethyl amine in the absence of a proton source is described. Both reductions, contrary to the reports of previous investigators, which indicated the 4-ene to be the main reaction product, gave a complex mixture of products. In the case of the reduction of 2, which is an intermediate in the synthesis of the progestagen desogestrel (1), we obtained the expected known 13-ethyl-gona-4-ene-11alpha,17beta-diol (4) in small amounts and three new steroidal monoenes, 13-ethyl-gona-5(10)-ene-11alpha,17beta-diol (11), 13-ethyl-gona-5(6)-ene-11alpha,17beta-diol (12), and 13-ethyl-gona-1(10)-ene-11alpha,17beta-diol (13). These compounds were characterized as the 11,17-diacetates with the 5(10)-ene 11 being the major compound.