The key intermediates for the synthesis of chiral oxetanes (3,5-di-O-benzyl-D-xylofurano-1,4-lactone, 3,5-di-O-benzyl-D-ribofurano-1,4-lactone, 3,5-di-O-benzyl-D-lyxofurano-1,4-lactone, 3,5-di-O-benzyl-D-arabinofurano-1, 4-lactone, and enantiomers of the corresponding lactones) were prepared in good yields by using the well-known procedures.
Each lactone was triflated and reacted with sodium methoxide to give the chiral oxetanes. Thus 3,5-di-O-benzyl-D-xylofurano-1,4-lactone and 3,5-di-Obenzyl-L-lyxofurano-1,4-lactone yielded a single oxetane, (2S, 3S, 4S)-2carbomethoxy-3-benzyloxy-4-benzyloxy methyl oxetane, in 92% and 82% yield, respectively. 3,5-Di-O-benzyl-L-xylofurano-1,4-lactone and 3,5-di-O-benzylL-lyxofurano-1,4-lactone also yielded a single oxetane, (2R, 3R, 4R)-2-carbomethoxy-3-benzyloxy-4-benzyloxymethyl-oxetnae, in 88% and 82% yield, respectively. 3,5-Di-O-benzyl-D-ribofurano-1,4-lactone produced ca. 8 : 1 mixture of (2R, 3R, 4S)-2-carbomethoxy-3-benzyloxy-4-benzyloxymethyl-oxetane and (2S,3R, 4S)-2-carbomethoxy-3-benzyloxy-4-benzyloxymethyl-oxetane in 77% yield. 3,5-Di-O-benzyl-D-arabinofurano-1,4-lactone gave ca. 20 : 1 mixture of the same products as above in 81% yield. 3,5-Di-O-benzyl-L-arabinofurano1,4-lactone gave ca. 20:1 mixture of (2S, 3S, 4R)-2-carbomethoxy-3-benzyloxy-4-benzyloxymethyl-oxetane and (2R, 3S, 4R)-2-carbomethoxy-3-benzyloxy4-benzyloxymethyl-oxetane in 79% yield. 3,5-Di-O-benzyl-L-ribofurano-1,4lactone also produced ca. 8:1 mixture of the same products as sbove in 72% yield. On the basis of the stereochemistry of the carbon which has a leaving group (triflyl), the above-mentioned results show that four lactones(D-xylo, L-xylo-, D-arabino-, L-arabino-) produce 'inversion' oxetanes and the other four lactones(D-lyxo-, L-lyxo-, D-ribo-, L-ribo-) produce 'retention' oxetanes predominantly. Therefore, the oxetane formation reaction appears not to be governed by the stereochemistry of the leaving group, but governed by the stereochemistry of the benzyloxy group at C-3 position of the lactones studied in this thesis.
이제까지 알려져 있지 않은 8가지의 락톤( 3,5-di-O-benzyl-Dxylofurano-1,4-lactone, 3,5-di-O-benzyl-D-ribofurano-1,4-lactone, 3,5-di-Obenzyl-L-xylofurano-1,4-lactone, 3,5-di-O-benzyl-L-ribofurano-1,4-lactone, 3,5-di-O-benzyl-D-lyxofurano-1,4-lactone, 3,5-di-O-benzyl-D-arabinofurano1,4-lactone, 3,5-di-O-benzyl-L-lyxofurano-1,4-lactone, and 3,5-di-O-benzylL-arabinofurano-1,4-lactone)들을 D-자이로즈와 L-자이로즈로 부터 이미 알려진 합성법들을 이용하여 좋은 수율로 합성하였다. 이 락톤들은 α 위치의 히드록시기를 트리플기로 만든다음 소디움 메톡시드와 메탄올에서 반응시켜 옥세탄 고리를 가진 화합물들을 합성하였다. 이때 토실이나 메실기를 이용하든지 나트륨 메톡시드 대신 탄산칼륨을 사용하면 수율이 낮아지거나 반응이 깨끗하지 않았다.
옥세탄 고리 화합물들은 모두 6가지가 얻어졌는데 (44, 45, 46, 47, 48, 49) 출발물들(락톤)과 생성물(옥세탄)들의 입체 화학을 비교하여 볼때, 이 반응이 진행되는 과정에서 생성물의 입체 화학은 이탈기의 입체 화학 보다는 이탈기의 바로 옆에 있는 3 번 위치 탄소의 벤질옥시기의 입체화학에 주로 의존되는 것으로 나타났다.
