Reactivity of biologically important reduced pyridines. IV. Effect of

J. Org. C h e m . 1989,54, 3721-3726 with assignments for 7). Anal. Calcd for CmH&lN&08: C, 61.29; H, 5.52; C1, 6.70; N, 5.30; S, 12.12. Found C, 61.30; H, 5.57; C1, 6.65; N, 5.23; S, 12.10. From 0-Silylated Hemithioacetal 10. The 0-silylated hemithioacetal reaction mixture as described above (ca.34 mmol of 10) was filtered, and the resulting CHzClzsolution was cooled to -50 "C. Methyl 3-mercaptopropionate (4.33 mL, 39.1 mmol) was added followed by dropwise addition of BF3.Eh0 (21.0 mL, 170 mmol) with mechanical stirring at