No abstract

This contribution describes the first stereospecific synthesis of 24(S)-hydroxyvitamin D2 (1), a metabolite of vitamin D2. This metabolite acts as a prodrug for 1α,24(S)-dihydroxyvitamin D2 (2), which is under development for treatment of various diseases characterized by cellular hyperproliferation. The key step of the synthesis involves the Wittig−Horner olefination of (S)-2,3-dimethyl-2-triethysilyloxybutyraldehyde (17) and a vitamin D2 phosphine oxide derivative (22). The synthesis of the requisite aldehyde started with the commercially available l-(+)-valine and was completed in seven steps. The vitamin D2 phosphine oxide derivative was synthesized in seven steps starting from vitamin D2.

Heating of allylic amide or allylic ester substituted diene-Fe(C0)3 complexes such as ( 7) and (10) (140°C) results in an intramolecular coupling of the pendant double bond with the diene moiety to give spirolactam and spirolactone derivatives; the stereochemical course of this reaction was established by an X-ray crystal structure determination of the lactone derivative (1 1).Carbon-carbon bond formation by addition of nucleophiles to a variety of organotransition metal complexes has resulted in wide-ranging synthetic application.1 Cationic dienyl-Fe( CO), complexes are very reactive toward nucleophiles and show considerable promise as synthetic intermediates,* but there are nevertheless many problems associated with their use. For example, the traditional hydride abstraction [e.g., (1) to (2)]

Excellent stereocontrol during the ene-type coupling between diene-Fe(C0I3 groups and alkenes can be achieved by appropriate substitution at C(5) of the diene ring, allowing the preparation of spirolactams and spirolactones in enantiomerically pure form, thus showing the cyclization reaction to be a valuable tool in the asymmetric construction of quaternary and spiro carbon centres.

In today's ever-increasing competition and regulatory restriction environment, it is critical for Ag-Chemical companies to have a sustained effort to explore and leverage novel and innovative technologies for more effective and efficient formulation and delivery systems. In recent years, nano-technology has been a particularly active area, and has shown the potential in enhancing bio-efficacy, bio-availability, and better penetration or uptake, especially for poorly soluble active ingredients. Our cellular uptake study demonstrated the penetration, uptake, and mobility of NPs in model cell systems. The subsequent hydroponic delivery study proved that NPs can transport through root and move upward through xylem. Several types of pesticide active ingredients were incorporated into nano-capsules. When compared to conventional micron-sized formulations, the nano-capsule formulations demonstrated significantly higher levels of activity. These studies indicate the potential for improving the effectiveness of agricultural active ingredients using nano-sized particles, including functionalized nano-capsules.