Efficient syntheses of a variety of labeled compounds from acetylene[¹⁴C₂]

Abstract

Acetylene[14C2] is shown to be a useful starting material for the synthesis of a number of 14C‐labeled intermediates and small molecules. Its facile preparation from inexpensive barium carbonate[14C] and the range of transformations it undergoes allow the efficient syntheses of 2‐propyn‐[2,3‐14C2]‐1‐ol, 2‐propen[2,3‐14C2]‐1‐ol, 2‐propen[G‐14C]yl‐isothiocyanate, 2‐butanone[1,2‐14C2], furan[3,4‐14C2], p‐dioxane[U‐14C], and various other intermediates.

Preparation of Carbon‐14‐Labeled Compounds via the [ 14 C 2 ]Acetylene Tree

“…Chain extension through aldol condensation with acetone and acid-catalyzed cyclization converted 7 to b- [6,7-14 C 2 ]ionone. Bis-hydroboration of [ 14 C 2 ]alkynol 9 with 9-borabicyclo[3.3.1]nonane, oxidative work up and hydrolytic cleavage of the carboxylic acid protecting group provided racemic [4,[5][6][7][8][9][10][11][12][13][14] C 2 ]mevalonolactone 6 (10). Bis-hydroboration of [ 14 C 2 ]alkynol 9 with 9-borabicyclo[3.3.1]nonane, oxidative work up and hydrolytic cleavage of the carboxylic acid protecting group provided racemic [4,[5][6][7][8][9][10][11][12][13][14] C 2 ]mevalonolactone 6 (10).…”

“…Its use as an essential starting material for the biological labeling of rapamycin in the metabolically stable positions 1,2,36,37 is a striking example and is discussed in Chapter 11, Section 11.3.6 9 . Their reaction with a-pyrones, for example, could furnish doubly labeled aromatic systems with well defined substitution patterns, as demonstrated by the synthesis of methyl [1,3,a- 13 Figure 8.8. Both compounds are synthetically accessible through carboxylation of the corresponding anionic species.…”