A unified, ready access to the tropoloisoquinoline alkaloids imerubrine (1), grandirubrine (2), and isoimerubrine (3) is delineated and features sequential application of the intramolecular Diels-Alder reaction of an acetylene-tethered oxazole and the [4 + 3] cycloaddition of an oxyallyl. A regioselective synthesis of 1 was achieved by stereo- and regioselective oxidation of an 8-oxabicyclo[3.2.1]oct-6-en-3-one cycloadduct by means of the Moriarty method. Such a post-cycloaddition functionalization complements the synthetic utility of an alpha-alkoxy-substituted oxyallyl so as to broaden the scope of the oxyallyl [4 + 3] cycloaddition reaction.

The hydroxy group regulates the stereoselectivity in a modification of the titanium‐mediated Kulinkovich cyclopropanation procedure (see scheme). This method provides a diastereoselective synthesis of trans‐1,2‐dialkylcyclopropanols, which starts with homoallylic alcohols and proceeds via a bicyclic titanacyclopropane intermediate. Enantiopure products may also be obtained if the corresponding chiral alcohols are used.

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-052Diastereoselective Synthesis of trans-1,2-Dialkylcyclopropanols by the Kulinkovich Hydroxycyclopropanation of Homoallylic Alcohols.-Title compounds are prepared in an enantio-and diastereoselective manner via bicyclic titanacyclopropane intermediates.