10.1039/c39850001388
The research focuses on the synthesis of (+)-milbemycin p3, an important compound in the field of organic chemistry. The purpose of the study was to develop a more practical and cost-effective alternative synthesis method compared to the previously reported directed aldol approach. The new method employed the 3,4-dihydro-2H-pyran approach, which was highly convergent and utilized inexpensive chiral precursors. Key steps in the synthesis included nucleophilic scission of oxirane by vinyl alanate and metallated 3,4-dihydro-2H-pyran. The chemicals used in the process included phenylthiomethyl-lithium, aldehyde (5), vinyl alanate (4), acetylene (3), and metallated 3,4-dihydro-2H-pyran (15), among others. The conclusions of the research indicated that all reactions could be performed on a substantial scale, yielding products that were easily purified, making this approach more practical than the directed aldol method. The study also highlighted the importance of stereoselective synthesis of the spiroacetal moiety and the C(14)-C(15) trisubstituted double bond in the overall synthesis process.