This invention relates to compounds of Formula (I):and pharmaceutically acceptable salts thereof, wherein Y1a, Y1b, Y2a, Y2b, Y3a, and Y3b are each independently selected from hydrogen and deuterium, Y4a, Y4b, Y5a, Y5b, Y6a, Y6b, Y7a, Y7b, Y8a, Y8b, Y9a, Y9b, Y10a, Y10b, Y11a, Y11b, Y12a, Y12b, Y13a, Y13b, Y14a, Y14b, Y15a, Y15b, Y16a, Y16b, Y17a, Y17b, Y18a, and Y18b are each deuterium, X1a, X1b, X2a, X2b, X3, X4a, X4b, X5, and X6 are each independently selected from hydrogen and deuterium; and R is CD3. This invention also provides compositions comprising a compound of this invention and the use of such compositions in methods of treating diseases and conditions that are beneficially treated by administering a viral DNA polymerase inhibitor.