The addition of dienes, diazomethane, and carbenoids to the manno-and ribo-configurated thio-YOlactones 1 and 2 was investigated. Thus, 1 (Scheme I ) reacted with 2,3-dimethylbutadiene (+ 4, 73%), cyclopentadiene (+ 5a/b 1:1,70%), cyclohexa-1,3-diene (+ 9ab 23,92%), and the electron-rich butadiene 6 (+ 7ab 3:1, 82%). Wheras 5a/b was separated by flash chromatography, 7a/b was desilylated leading to the thiapyranone 8. Selective hydrolysis of one isopropylidene group of 9a/b and flash chromatography gave 10a and lob. The stuctures of the adducts were elucidated by X-ray analysis (4), by NOE experiments (4, 5a, Sb, 7a/ b, 10a, and lob), and on the basis of a homoallylic coupling (7a/b). The additions occurred selectively from the 'em'-side of 1. Only a weak preference for the 'endo'-adducts was observed. Hydrogenation of 9a/b with RaneyNi (EtOH, room temperature) gave the thiabicyclo[2.2.2]octane 11. Under harsher conditions (dioxane, 1 loo), 9a/b was reduced to the cyclohexyl /h-C-gIycoside 12 which was deprotected to 13. X-Ray analysis of 13 proved that the desulfuration occurred with inversion of the anomeric configuration. The regioselective addition of the dihydropyridine 14 to 1 (Scheme 2) and the metbanolysis of the crude adduct 15 gave the lactams 16a (32%) and 16b (38%). Desilylation of 15 with Bu,NF. 3H,O, however, gave the unsaturated piperidinedione 17 (92%) which was deprotected to the tetrol18 (65%). Similarly, 2 was transformed via 19 (62%) into the trio1 20 (74%). The cycloaddition of 1 with CH,N, (Scheme 3 ) gave a 35:65 mixture of the 2,5-dihydro-l,3,4-triazole 21 and the crystalline 4,5-dihydro-l,2,3-triazole 22. Treatment of 21 and 22 with base gave the hydroxytriazoles 23 and 24, respectively. The structure of 24 was established by X-ray analysis. The triazole mixture 21/22 was separated by prep. HPLC at 5'. At room temperature, 21 already decomposed (half-life 21.6 h) leading in CDCI, solution to a complex mixture (containing ca. 20-25% of the spirothiirane 27 and ca. 7-10% of its anomer) and in MeOH solution exclusively to the O,O,S-ortholactone 26. Crystals of 22 proved be stable at 105'. Upon heating in petroleum ether at looo, 22 was transformed into a ca. 1: 1 mixture of 27 and the enol ether 28. The reaction of 1 with ethyl diazoacetate (Scheme 4 ) in the presence of q ( 0 A c ) ; 2H,O gave the unsaturated esters 29 (33%) and 30 (26%), whereas the analogous reaction with diethyl diazomalonate afforded the spirothiirane 31 (68%) and the enol ether 32 (29%). Complete transformation of 31 into 32 was achieved by the treatment with P(NEt,),. Similarly, 33 (69%) was prepared from 2.
