Enantioselective Synthesis of the Unsaturated Fragment of Callyspongiolide.

A synthesis of the unsaturated side chain of callyspongiolide has been accomplished from two chiral building blocks prepared by catalytic asymmetric procedures applied on simple starting materials. The synthesis of the chiral benzylic alcohol was based on an enantioselective aldol reaction of a substituted benzaldehyde catalyzed by a chiral amine, whereas the chiral homoallyl alcohol was prepared by the enantioselective crotylboration of iodomethacryl aldehyde catalyzed by a chiral phosphoric acid. Both fragments were joined together by using standard Sonogashira coupling conditions.

Enantioselective Allylation of (2E,4E)-2,4-Dimethylhexadienal: Synthesis of (5R,6S)-(+)-Pteroenone.

Allylation, trans- and cis-crotylation of (2E,4E)-2,4-dimethylhexadienal, a representative α,ß,γ,δ-unsaturated aldehyde, was carried out under different catalytic and stoichiometric conditions. The reactions catalyzed by organocatalysts TRIP-PA and N,N'-dioxides gave the best results with respect to yields, asymmetric induction, and catalyst load in comparison to other procedures. The developed methodology was applied in the enantioselective synthesis of (5R,6S)-(+)-pteroenone, a defensive metabolite (ichthyodeterrent) of the Antarctic pteropod Clione antarctica.

Highly unstable sequence interruptions of the CTG repeat in the myotonic dystrophy gene.

Myotonic dystrophy type 1 is caused by the expansion of a CTG repeat in the 3' UTR of the DMPK gene. A length exceeding 50 CTG triplets is pathogenic. Intermediate alleles with 35-49 triplets are not disease-causing but show instability in intergenerational transmissions. We report on the identification of multiple patients with different patterns of CCG and CTC interruptions in the DMPK CTG repeat tract that display unique intergenerational instability. In patients bearing interrupted expanded alleles, the location of the interruptions changed dramatically between generations and the repeats tended to contract. The phenotype for these patients corresponded to the classical form of the disease, but in some cases without muscular dystrophy and possibly with a later onset than expected. Symptomatic patients bearing interrupted intermediate length repeat tracts were also identified, although the role of the interruptions in their phenotype remains unclear. The identification of interruptions in the DMPK repeat has important consequences for molecular genetic testing where they can lead to false negative conclusions.