The Belgium international was high on the Hammers' wishlist after an impressive first half to the campaign for his club side, which included six outings in the Champions League group stage.
West Ham are understood to have seen a deadline-day approach knocked back by Anderlecht, but will reportedly revive their interest in the defensive midfielder once the transfer window reopens at the end of the campaign.
Dendoncker did not expect terms to be agreed between the two clubs so late in the window, and admits to being 'greatly disappointed' at Anderlecht's refusal to let him leave last summer like they did with Youri Tielemans.
"If deals still have to be arranged in the evening on January 31, there is little chance that there will be a breakthrough," he told Het Laatste Nieuws. "West Ham seemed to me, however, a nice club to take the next step in my career.
"The disappointment [last summer] was great - I could barely overcome it. I noticed that after the departure of Youri they did not want to get rid of the whole midfield. I was on the phone every day with my agent. I was told, 'Be patient, it will come around, maybe at the very end.
"I was constantly working on that transfer, instead of just focusing on the training. I was wrong, I realise that. But it was the first time I came into such a situation, I just did not know how to deal with it."