Scheme 4: Synthesis of bivalent analogues of DMH-D-053 (63). Reagents and Conditions. (a) 2 N NaOH, EtOH, and reflux; (b) 10% aq. HCl; (c) CDI, DMF; (d) diol, DBU; (e) trimethylsilylacetylene, Pd(OAc)2(PPH3)2, Et3N, CH3CN, and reflux; (f) TBAF0.5H2O, THF, −78°C.