Non-growing, washed cells of Escherichia coli, depressed for the synthesis of thiamine, were incubated in the presence of [1,1,1 ,5-ZH4]-1 -deoxy-D-threo-2-pentulose (9) in a medium containing the pyrimidine moiety of thiamine, L-tyrosine, and glucose. The thiamine thus biosynthesized was extracted and cleaved to give 5-(2hydroxyethyl) -4-methylthiazole (H ET) which was examined as the trifluoroacetate derivative by electron-impact mass spectrometry. The dist:ibution of the label in the fragments indicated that the pentulose (9) was a precursor of the C,-chain of HET without C-C bond cleavage. Several routes to 1 -deoxypentuloses are described. Condensation of 2,4-O-benzylidene-D-[4-2H ,]threose (23) with trideuteriomethylmagnesium iodide gave the protected 1 -deoxypentitols ( 24) and ( 25). Brominolysis of the mixed dibutylstannylidenes then afforded [l,l,l ,5-2H4]-3,5-O-benzylidene-l -deoxy-D-threo-2-pentulose (26), which was converted into the free sugar (9) by acidic hydrolysis. 1 -Deoxy-D-erythro-2-pentulose was prepared in similar manner. Condensation of 2-( [2H3]methyl) -1,3-dithian with 2,3-O-isopropylidene-D-glyceraldehyde, followed by a C-3 epimerization step also led, after deprotection, to a mixture of [1,1,1 -2H3]-1 -deoxy-D-eryfhro-and [1,1,1 -2H3]-1 -deoxy-D-threo-2-pentulose, (5) and (6).
