Abstract: The stereochemistry of the reactions of substituted allylboronates 5-9 with D- glyceraldehyde acetonide (4) and L-4-deoxythreose cyclohexyl ketal (2) is described. The reactions involving (Z)-crotylboronates 5 and 6 are exceptionally stereoselective, with selectivity for the major 3, 4-syn, 4, 5-anti adducts 19, 23, 27, and 31 approaching the limit defined by the isomeric purity of the reagents. The level of aldehyde diastereofacial ...