Functionalised Monocyclic Five- to Seven-Memberedexo-Glycals by Alkynol Cycloisomerisation of Hydroxy Buta-1,3-diynes and 1-Haloalkynols
作者:Ming Xu、Zhiwei Miao、Bruno Bernet、Andrea Vasella
DOI:10.1002/hlca.200590235
日期:2005.11
glucose, and mannose hemiacetals by ethynylation. The hex-1-ynitol 2 derived from 1 (61%) was transformed via the 1-phenylbuta-1,3-diyne 3 and the 1-(pyridin-2-yl)acetylene 5 into the five-membered exo-glycals 4 and 6 (in 66 and 72% yields, resp., from 2). The analoguous ethynylation of 2,3,4,6-tetra-O-benzyl-D-galactose 8 was accompanied by elimination of one benzyloxy (BnO) group to the hept-3-en-1-ynitol
部分苄基化,1-取代的(R = PhCC,吡啶-2-基或Br)醛-1-炔醇的碱促进(KOH或MeONa在MeOH中,或NaH在THF中)环异构化导致形成(Z)-构型的五个-,六元和七元exo-糖。醛-1-炔醇的反应性取决于它们的构型。醛-1-炔醇通过乙炔基化衍生自2,3,5-三-O-苄基-D-呋喃呋喃糖1和相应的部分被O-苄基化的半乳糖,葡萄糖和甘露糖半缩醛。衍生自1(61%)的hex-1-ynitol 2通过1-苯基丁-1,3-二炔3和1-(吡啶-2-基)乙炔5转化进入五元外糖4和6(分别从2到66和72%的产率)。2,3,4,6-四-O-苄基-D-半乳糖8的类似乙炔基化反应伴随着一个庚氧基(BnO)基团被消除到庚-3-烯-1-炔醇9(71%)上,将其转化为非5-烯-1,3-二炔醇10,并进一步转化为六元外糖基11(9的50%)。另外的Me 3 SiCCH到半乳糖8和对葡萄糖-和甘露-a