Optically active polyhydroxy trans-1,2-amino alcohols were efficiently synthesized in good to excellent yields by the Petasis boronic-Mannich reaction of an amine, an organoboronic acid, and a chiral lactol, which was prepared from D-araboascorbic acid or its diastereomer. Further transformations of the resulting Petasis products were investigated in detail to obtain chiral building blocks containing three continuous stereogenic centers.

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The rate of the intramolecular Morita-Baylis-Hillman (MBH) reaction is remarkably enhanced by the combination of catalytic amounts of a nucleophilic catalyst (4-dimethylaminopyridine (DMAP), 4-pyrrolidinopyridine (PPY), or PBu 3 ) and 1,3-diphenyl-2-thiourea, and the desired MBH adducts are obtained in good to high yields within a few hours.The Morita-Baylis-Hillman (MBH) reaction has been widely studied over the past 40 years, and is recognized as one of the most useful transformations in synthetic organic chemistry. [1] Reactions with a tertiary amine or phosphine as an activator give densely functionalized products, which can be extensively used for further transformations. [1g, 2] However, the MBH reaction typically requires a large excess of either substrate in intermolecular reactions (> 3 equiv.), a stoichiometric amount of activator or higher catalyst loading (> 20 mol %), and a longer reaction time (typically > 24 h) to achieve synthetically useful yields of the products with a limited scope of the substrates. To address these drawbacks, enhancement of the rate of MBH reactions has been extensively studied. Maher and Connon

Remarkable Enhancement of the Rate of the Intramolecular Morita-Baylis--Hillman Reaction by the Combination of a Nucleophilic Catalyst and 1,3-Diphenyl-2-thiourea. -(MANDAI, H.; SHIMOWAKI, K.; MITSUDO, K.; SUGA*, S.; Asian J. Org. Chem. 3 (2014) 4, 437-441, http://dx.